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<h1 class="settitle">Liblouis User's and Programmer's Manual</h1>
<div class="contents">
<h2>Table of Contents</h2>
<ul>
<li><a name="toc_Top" href="#Top">Liblouis User's and Programmer's Manual</a>
<li><a name="toc_Introduction" href="#Introduction">1 Introduction</a>
<li><a name="toc_Test-Programs" href="#Test-Programs">2 Test Programs</a>
<ul>
<li><a href="#lou_005fdebug">2.1 lou_debug</a>
<li><a href="#lou_005fchecktable">2.2 lou_checktable</a>
<li><a href="#lou_005fallround">2.3 lou_allround</a>
<li><a href="#lou_005ftranslate-_0028program_0029">2.4 lou_translate</a>
<li><a href="#lou_005fcheckhyphens">2.5 lou_checkhyphens</a>
</li></ul>
<li><a name="toc_How-to-Write-Translation-Tables" href="#How-to-Write-Translation-Tables">3 How to Write Translation Tables</a>
<ul>
<li><a href="#Hyphenation-Tables">3.1 Hyphenation Tables</a>
<li><a href="#Character_002dDefinition-Opcodes">3.2 Character-Definition Opcodes</a>
<li><a href="#Braille-Indicator-Opcodes">3.3 Braille Indicator Opcodes</a>
<li><a href="#Emphasis-Opcodes">3.4 Emphasis Opcodes</a>
<li><a href="#Special-Symbol-Opcodes">3.5 Special Symbol Opcodes</a>
<li><a href="#Special-Processing-Opcodes">3.6 Special Processing Opcodes</a>
<li><a href="#Translation-Opcodes">3.7 Translation Opcodes</a>
<li><a href="#Character_002dClass-Opcodes">3.8 Character-Class Opcodes</a>
<li><a href="#Swap-Opcodes">3.9 Swap Opcodes</a>
<li><a href="#The-Context-and-Multipass-Opcodes">3.10 The Context and Multipass Opcodes</a>
<li><a href="#The-correct-Opcode">3.11 The correct Opcode</a>
<li><a href="#Miscellaneous-Opcodes">3.12 Miscellaneous Opcodes</a>
<li><a href="#Deprecated-Opcodes">3.13 Deprecated Opcodes</a>
</li></ul>
<li><a name="toc_Notes-on-Back_002dTranslation" href="#Notes-on-Back_002dTranslation">4 Notes on Back-Translation</a>
<li><a name="toc_Programming-with-liblouis" href="#Programming-with-liblouis">5 Programming with liblouis</a>
<ul>
<li><a href="#License">5.1 License</a>
<li><a href="#Overview">5.2 Overview</a>
<li><a href="#Data-structure-of-liblouis-tables">5.3 Data structure of liblouis tables</a>
<li><a href="#lou_005fversion">5.4 lou_version</a>
<li><a href="#lou_005ftranslateString">5.5 lou_translateString</a>
<li><a href="#lou_005ftranslate">5.6 lou_translate</a>
<li><a href="#lou_005fbackTranslateString">5.7 lou_backTranslateString</a>
<li><a href="#lou_005fbackTranslate">5.8 lou_backTranslate</a>
<li><a href="#lou_005fhyphenate">5.9 lou_hyphenate</a>
<li><a href="#lou_005fcompileString">5.10 lou_compileString</a>
<li><a href="#lou_005fdotsToChar">5.11 lou_dotsToChar</a>
<li><a href="#lou_005fcharToDots">5.12 lou_charToDots</a>
<li><a href="#lou_005flogFile">5.13 lou_logFile</a>
<li><a href="#lou_005flogPrint">5.14 lou_logPrint</a>
<li><a href="#lou_005flogEnd">5.15 lou_logEnd</a>
<li><a href="#lou_005fsetDataPath">5.16 lou_setDataPath</a>
<li><a href="#lou_005fgetDataPath">5.17 lou_getDataPath</a>
<li><a href="#lou_005fgetTable">5.18 lou_getTable</a>
<li><a href="#lou_005freadCharFromFile">5.19 lou_readCharFromFile</a>
<li><a href="#lou_005ffree">5.20 lou_free</a>
<li><a href="#Python-bindings">5.21 Python bindings</a>
</li></ul>
<li><a name="toc_Opcode-Index" href="#Opcode-Index">Opcode Index</a>
<li><a name="toc_Function-Index" href="#Function-Index">Function Index</a>
<li><a name="toc_Program-Index" href="#Program-Index">Program Index</a>
</li></ul>
</div>
<p><a name="Top"></a>
<h2 class="unnumbered">Liblouis User's and Programmer's Manual</h2>
<p>This manual is for liblouis (version 2.3.0, 9 May 2011),
a Braille Translation and Back-Translation Library derived from the
Linux screen reader <acronym>BRLTTY</acronym>.
<p class="noindent">Copyright © 1999-2006 by the BRLTTY Team.
<p class="noindent">Copyright © 2004-2007 ViewPlus Technologies, Inc.
<a href="www.viewplus.com">www.viewplus.com</a>.
<p class="noindent">Copyright © 2007,2009 Abilitiessoft, Inc.
<a href="www.abilitiessoft.com">www.abilitiessoft.com</a>.
<blockquote>
This file is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser (or library) General Public License
(LGPL) as published by the Free Software Foundation; either version 3,
or (at your option) any later version.
<p>This file is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser (or Library) General Public License LGPL for more details.
<p>You should have received a copy of the GNU Lesser (or Library) General
Public License (LGPL) along with this program; see the file COPYING.
If not, write to the Free Software Foundation, 51 Franklin Street,
Fifth Floor, Boston, MA 02110-1301, USA.
</blockquote>
<p><a name="Introduction"></a>
<h2 class="chapter">1 Introduction</h2>
<p>Liblouis is an open-source braille translator and back-translator
derived from the translation routines in the BRLTTY screen reader for
Linux. It has, however, gone far beyond these routines. It is named in
honor of Louis Braille. In Linux and Mac OSX it is a shared library,
and in Windows it is a DLL. For installation instructions see the
README file. Please report bugs and oddities to the maintainer,
<a href="mailto:john.boyer@abilitiessoft.com">john.boyer@abilitiessoft.com</a>
<p>This documentation is derived from Chapter 7 of the BRLTTY manual, but
it has been extensively rewritten to cover new features.
<p>Please read the following copyright and warranty information. Note
that this information also applies to all source code, tables and
other files in this distribution of liblouis. It applies similarly to
the sister library liblouisxml.
<p>This file is maintained by John J. Boyer
<a href="mailto:john.boyer@abilitiessoft.com">john.boyer@abilitiessoft.com</a>.
<p>Persons who wish to program with liblouis but will not be writing
translation tables may want to skip ahead to <a href="#Programming-with-liblouis">Programming with liblouis</a>.
<p><a name="Test-Programs"></a>
<h2 class="chapter">2 Test Programs</h2>
<p>Five test programs are provided as part of the liblouis package. They
are intended for testing liblouis and for debugging tables. None of
them is suitable for braille transcription. An application that can be
used for transcription is <samp><span class="command">xml2brl</span></samp>, which is part of the
liblouisxml package (see <a href="liblouisxml.html#Top">Introduction</a>). The source code of the
test programs can be studied to learn how to use the liblouis library
and they can be used to perform the following functions.
<p><a name="common-options"></a>All of these programs recognize the <samp><span class="option">--help</span></samp> and
<samp><span class="option">--version</span></samp> options.
<dl>
<dt><samp><span class="option">--help</span></samp><dt><samp><span class="option">-h</span></samp><dd>Print a usage message listing all available options, then exit
successfully.
<br><dt><samp><span class="option">--version</span></samp><dt><samp><span class="option">-v</span></samp><dd>Print the version number, then exit successfully.
</dl>
<p><a name="lou_debug"></a>
<a name="lou_005fdebug"></a>
<h3 class="section">2.1 lou_debug</h3>
<p><a name="index-lou_005fdebug-1"></a>
The lou_debug tool is intended for debugging liblouis translation
tables. The command line for lou_debug is:
<pre class="example"> lou_debug [OPTIONS] TABLE[,TABLE,...]
</pre>
<p>The command line options that are accepted by lou_debug are described
in <a href="#common-options">common options</a>.
<p>The table (or comma-separated list of tables) is compiled. If no
errors are found a brief command summary is printed, then the prompt
‘<samp><span class="samp">Command:</span></samp>’. You can then input one of the command letters and get
output, as described below.
<p>Most of the commands print information in the various arrays of
<code>TranslationTableHeader</code>. Since these arrays are pointers to
chains of hashed items, the commands first print the hash number, then
the first item, then the next item chained to it, and so on. After
each item there is a prompt indicated by ‘<samp><span class="samp">=></span></samp>’. You can then press
enter (<kbd><RET></kbd>) to see the next item in the chain or the first
item in the next chain. Or you can press <kbd>h</kbd> (for next-(h)ash) to
skip to the next hash chain. You can also press <kbd>e</kbd> to exit the
command and go back to the ‘<samp><span class="samp">command:</span></samp>’ prompt.
<dl>
<dt><kbd>h</kbd><dd>Brings up a screen of somewhat more extensive help.
<br><dt><kbd>f</kbd><dd>Display the first forward-translation rule in the first non-empty hash
bucket. The number of the bucket is displayed at the beginning of the
chain. Each rule is identified by the word ‘<samp><span class="samp">Rule:</span></samp>’. The fields
are displayed by phrases consisting of the name of the field, an equal
sign, and its value. The before and after fields are displayed only if
they are nonzero. Special opcodes such as the <code>correct</code> opcode (see <a href="#correct-opcode">correct</a>) and
the multipass opcodes are shown with the code that instructs the
virtual machine that interprets them. If you want to see only the
rules for a particular character string you can type <kbd>p</kbd> at the
‘<samp><span class="samp">command:</span></samp>’ prompt. This will take you to the ‘<samp><span class="samp">particular:</span></samp>’
prompt, where you can press <kbd>f</kbd> and then type in the string. The
whole hash chain containing the string will be displayed.
<br><dt><kbd>b</kbd><dd>Display back-translation rules. This display is very similar to that
of forward translation rules except that the dot pattern is displayed
before the character string.
<br><dt><kbd>c</kbd><dd>Display character definitions, again within their hash chains.
<br><dt><kbd>d</kbd><dd>Displays single-cell dot definitions. If a character-definition opcode
gives a multi-cell dot pattern, it is displayed among the
back-translation rules.
<br><dt><kbd>C</kbd><dd>Display the character-to-dots map. This is set up by the
character-definition opcodes and can also be influenced by the
<code>display</code> opcode (see <a href="#display-opcode">display</a>).
<br><dt><kbd>D</kbd><dd>Display the dot to character map, which shows which single-cell dot
patterns map to which characters.
<br><dt><kbd>z</kbd><dd>Show the multi-cell dot patterns which have been assigned to the
characters from 0 to 255 to comply with computer braille codes such as
a 6-dot code. Note that the character-definition opcodes should use
8-dot computer braille.
<br><dt><kbd>p</kbd><dd>Bring up a secondary (‘<samp><span class="samp">particular:</span></samp>’) prompt from which you can
examine particular character strings, dot patterns, etc. The commands
(given in its own command summary) are very similar to those of the
main ‘<samp><span class="samp">command:</span></samp>’ prompt, but you can type a character string or
dot pattern. They include <kbd>h</kbd>, <kbd>f</kbd>, <kbd>b</kbd>, <kbd>c</kbd>, <kbd>d</kbd>,
<kbd>C</kbd>, <kbd>D</kbd>, <kbd>z</kbd> and <kbd>x</kbd> (to exit this prompt), but not
<kbd>p</kbd>, <kbd>i</kbd> and <kbd>m</kbd>.
<br><dt><kbd>i</kbd><dd>Show braille indicators. This shows the dot patterns for various
opcodes such as the <code>capsign</code> opcode (see <a href="#capsign-opcode">capsign</a>) and the <code>numsign</code> opcode (see <a href="#numsign-opcode">numsign</a>).
It also shows emphasis dot patterns, such as those for the
<!-- FIXME: the italword opcode should be documented -->
<!-- @opcoderef{italword}, -->
<code>italword</code>,
the <code>firstletterbold</code> opcode (see <a href="#firstletterbold-opcode">firstletterbold</a>), etc. If a given
opcode has not been used nothing is printed for it.
<br><dt><kbd>m</kbd><dd>Display various miscellaneous information about the table, such as the
number of passes, whether certain opcodes have been used, and whether
there is a hyphenation table.
<br><dt><kbd>q</kbd><dd>Exit the program.
</dl>
<p><a name="lou_checktable"></a>
<a name="lou_005fchecktable"></a>
<h3 class="section">2.2 lou_checktable</h3>
<p><a name="index-lou_005fchecktable-2"></a>
To use this program type the following:
<pre class="example"> lou_checktable [OPTIONS] TABLE
</pre>
<p>Aside from the standard options (see <a href="#common-options">common options</a>) lou_checktable
also accepts the following options:
<dl>
<dt><samp><span class="option">--quiet</span></samp><dt><samp><span class="option">-q</span></samp><dd>Do not write to standard error if there are no errors.
</dl>
<p>If the table contains errors, appropriate messages will be displayed.
If there are no errors the message ‘<samp><span class="samp">no errors found.</span></samp>’ will be
shown.
<p><a name="lou_allround"></a>
<a name="lou_005fallround"></a>
<h3 class="section">2.3 lou_allround</h3>
<p><a name="index-lou_005fallround-3"></a>
This program tests every capability of the liblouis library. It is
completely interactive. Invoke it as follows:
<pre class="example"> lou_allround [OPTIONS]
</pre>
<p>The command line options that are accepted by lou_debug are described
in <a href="#common-options">common options</a>.
<p>You will see a few lines telling you how to use the program. Pressing
one of the letters in parentheses and then enter will take you to a
message asking for more information or for the answer to a yes/no
question. Typing the letter ‘<samp><span class="samp">r</span></samp>’ and then <RET> will take you
to a screen where you can enter a line to be processed by the library
and then view the results.
<p><a name="lou_translate-(program)"></a>
<a name="lou_005ftranslate-_0028program_0029"></a>
<h3 class="section">2.4 lou_translate</h3>
<p><a name="index-lou_005ftranslate-4"></a>
This program translates whatever is on the standard input unit and
prints it on the standard output unit. It is intended for large-scale
testing of the accuracy of translation and back-translation. The
command line for lou_translate is:
<pre class="example"> lou_translate [OPTION] TABLE
</pre>
<p>Aside from the standard options (see <a href="#common-options">common options</a>) this program
also accepts the following options:
<dl>
<dt><samp><span class="option">--forward</span></samp><dt><samp><span class="option">-f</span></samp><dd>Do a forward translation.
<br><dt><samp><span class="option">--backward</span></samp><dt><samp><span class="option">-b</span></samp><dd>Do a backward translation.
</dl>
<p>To use it to translate or back-translate a file use a line like
<pre class="example"> lou_translate --forward en-us-g2.ctb <liblouis.txt >testtrans
</pre>
<p><a name="lou_checkhyphens"></a>
<a name="lou_005fcheckhyphens"></a>
<h3 class="section">2.5 lou_checkhyphens</h3>
<p><a name="index-lou_005fcheckhyphens-5"></a>
This program checks the accuracy of hyphenation in Braille translation
for both translated and untranslated words. It is completely
interactive. Invoke it as follows:
<pre class="example"> lou_checkhyphens [OPTIONS]
</pre>
<p>The command line options that are accepted by lou_checkhyphens are
described in <a href="#common-options">common options</a>.
<p>You will see a few lines telling you how to use the program.
<p><a name="How-to-Write-Translation-Tables"></a>
<h2 class="chapter">3 How to Write Translation Tables</h2>
<p>Many translation (contraction) tables have already been made up. They
are included in this distribution in the tables directory and should be
studied as part of the documentation. The most helpful (and normative)
are listed in the following table:
<dl>
<dt><samp><span class="file">chardefs.cti</span></samp><dd>Character definitions for U.S. tables
<br><dt><samp><span class="file">compress.ctb</span></samp><dd>Remove excessive whitespace
<br><dt><samp><span class="file">en-us-g1.ctb</span></samp><dd>Uncontracted American English
<br><dt><samp><span class="file">en-us-g2.ctb</span></samp><dd>Contracted or Grade 2 American English
<br><dt><samp><span class="file">en-us-brf.dis</span></samp><dd>Make liblouis output conform to BRF standard
<br><dt><samp><span class="file">en-us-comp8.ctb</span></samp><dd>8-dot computer braille for use in coding examples
<br><dt><samp><span class="file">en-us-comp6.ctb</span></samp><dd>6-dot computer braille
<br><dt><samp><span class="file">nemeth.ctb</span></samp><dd>Nemeth Code translation for use with liblouisxml
<br><dt><samp><span class="file">nemeth_edit.ctb</span></samp><dd>Fixes errors at the boundaries of math and text
</dl>
<p>The names used for files containing translation tables are completely
arbitrary. They are not interpreted in any way by the translator.
Contraction tables may be 8-bit ASCII files, 16-bit big-endian Unicode
files or 16-bit little-endian Unicode files. Blank lines are ignored.
Any leading and trailing whitespace (any number of blanks and/or tabs)
is ignored. Lines which begin with a number sign or hatch mark
(‘<samp><span class="samp">#</span></samp>’) are ignored, i.e. they are comments. If the number sign is
not the first non-blank character in the line, it is treated as an
ordinary character. If the first non-blank character is less-than
(‘<samp><span class="samp"><</span></samp>’) the line is also treated as a comment. This makes it possible
to mark up tables as xhtml documents. Lines which are not blank or
comments define table entries. The general format of a table entry is:
<pre class="example"> opcode operands comments
</pre>
<p>Table entries may not be split between lines. The opcode is a mnemonic
that specifies what the entry does. The operands may be character
sequences, braille dot patterns or occasionally something else. They
are described for each opcode, please see <a href="#Opcode-Index">Opcode Index</a>. With some
exceptions, opcodes expect a certain number of operands. Any text on
the line after the last operand is ignored, and may be a comment. A
few opcodes accept a variable number of operands. In this case a
number sign begins a comment unless it is preceded by a backslash
(‘<samp><span class="samp">\</span></samp>’).
<p>Here are some examples of table entries.
<pre class="example"> # This is a comment.
always world 456-2456 A word and the dot pattern of its contraction
</pre>
<p>Most opcodes have both a "characters" operand and a "dots" operand,
though some have only one and a few have other types.
<p>The characters operand consists of any combination of characters and
escape sequences proceeded and followed by whitespace. Escape
sequences are used to represent difficult characters. They begin with
a backslash (`\`). They are:
<dl>
<dt><kbd>\</kbd><dd>backslash
<br><dt><kbd>\f</kbd><dd>form feed
<br><dt><kbd>\n</kbd><dd>new line
<br><dt><kbd>\r</kbd><dd>carriage return
<br><dt><kbd>\s</kbd><dd>blank (space)
<br><dt><kbd>\t</kbd><dd>horizontal tab
<br><dt><kbd>\v</kbd><dd>vertical tab
<br><dt><kbd>\e</kbd><dd>"escape" character (hex 1b, dec 27)
<br><dt><kbd>\xhhhh</kbd><dd>4-digit hexadecimal value of a character
</dl>
<p>If liblouis has been compiled for 32-bit Unicode the following are
also recognized.
<dl>
<dt><kbd>\yhhhhh</kbd><dd>5-digit (20 bit) character
<br><dt><kbd>\zhhhhhhhh</kbd><dd>Full 32-bit value.
</dl>
<p>The dots operand is a braille dot pattern. The real braille dots, 1
through 8, must be specified with their standard numbers. liblouis
recognizes "virtual dots," which are used for special purposes, such
as distinguishing accent marks. There are seven virtual dots. They are
specified by the number 9 and the letters ‘<samp><span class="samp">a</span></samp>’ through ‘<samp><span class="samp">f</span></samp>’.
For a multi-cell dot pattern, the cell specifications must be
separated from one another by a dash (‘<samp><span class="samp">-</span></samp>’). For example, the
contraction for the English word ‘<samp><span class="samp">lord</span></samp>’ (the letter ‘<samp><span class="samp">l</span></samp>’
preceded by dot 5) would be specified as 5-123. A space may be
specified with the special dot number 0.
<p>An opcode which is helpful in writing translation tables is
<code>include</code>. Its format is:
<pre class="example"> include filename
</pre>
<p>It reads the file indicated by <code>filename</code> and incorporates or
includes its entries into the table. Included files can include other
files, which can include other files, etc. For an example, see what
files are included by the entry <code>include en-us-g1.ctb</code> in the table
<samp><span class="file">en-us-g2.ctb</span></samp>. If the included file is not in the same directory
as the main table, use a full path name for filename. Tables can also be
specified in a table list, in which the table names are separated by
commas and given as a single table name in calls to the translation
functions.
<p>The order of the various types of opcodes or table entries is
important. Character-definition opcodes should come first. However, if
the optional <code>display</code> opcode (see <a href="#display-opcode">display</a>) is used it should precede
character-definition opcodes. Braille-indicator opcodes should come
next. Translation opcodes should follow. The <code>context</code> opcode (see <a href="#context-opcode">context</a>) is a
translation opcode, even though it is considered along with the
multipass opcodes. These latter should follow the translation opcodes.
The <code>correct</code> opcode (see <a href="#correct-opcode">correct</a>) can be used anywhere after the
character-definition opcodes, but it is probably a good idea to group
all <code>correct</code> opcodes together. The <code>include</code> opcode (see <a href="#include-opcode">include</a>) can be
used anywhere, but the order of entries in the combined table must
conform to the order given above. Within each type of opcode, the
order of entries is generally unimportant. Thus the translation
entries can be grouped alphabetically or in any other order that is
convenient. Hyphenation tables may be specified either with an
<code>include</code> opcode or as part of a table list. They should come after
everything else. Character-definition opcodes are necessary for
hyphenation tables to work.
<p><a name="Hyphenation-Tables"></a>
<h3 class="section">3.1 Hyphenation Tables</h3>
<p>Hyphenation tables are necessary to make opcodes such as the
<code>nocross</code> opcode (see <a href="#nocross-opcode">nocross</a>) function properly. There are no opcodes for
hyphenation table entries because these tables have a special format.
Therefore, they cannot be specified as part of an ordinary table.
Rather, they must be included using the <code>include</code> opcode (see <a href="#include-opcode">include</a>) or as part
of a table list. The liblouis hyphenation algorithm was adopted from the
one used by OpenOffice. Note that Hyphenation tables must follow
character definitions and should preferably be the last. For an example
of a hyphenation table, see <samp><span class="file">hyph_en_US.dic</span></samp>.
<p><a name="Character-Definition-Opcodes"></a>
<a name="Character_002dDefinition-Opcodes"></a>
<h3 class="section">3.2 Character-Definition Opcodes</h3>
<p>These opcodes are needed to define attributes such as digit,
punctuation, letter, etc. for all characters and their dot patterns.
liblouis has no built-in character definitions, but such definitions
are essential to the operation of the <code>context</code> opcode (see <a href="#context-opcode">context</a>), the
<code>correct</code> opcode (see <a href="#correct-opcode">correct</a>), the multipass opcodes and the back-translator. If
the dot pattern is a single cell, it is used to define the mapping
between dot patterns and characters, unless a <code>display</code> opcode (see <a href="#display-opcode">display</a>) for
that character-dot-pattern pair has been used previously. If only a
single-cell dot pattern has been given for a character, that dot
pattern is defined with the character's own attributes. If more than
one cell is given and some of them have not previously been defined as
single cells, the undefined cells are entered into the dots table with
the space attribute. This is done for backward compatibility with
old tables, but it may cause problems with the above opcodes or
back-translation. For this reason, every single-cell dot pattern
should be defined before it is used in a multi-cell character
representation. The best way to do this is to use the 8-dot computer
braille representation for the particular braille code. If a character
or dot pattern used in any rule, except those with the <code>display</code>
opcode, the <code>repeated</code> opcode (see <a href="#repeated-opcode">repeated</a>) or the <code>replace</code> opcode (see <a href="#replace-opcode">replace</a>), is not
defined by one of the character-definition opcodes, liblouis will give
an error message and refuse to continue until the problem is fixed. If
the translator or back-translator encounters an undefined character in
its input it produces a succinct error indication in its output, and
the character is treated as a space.
<a name="index-space-6"></a>
<dl><a name="space-opcode"></a><dt><code>space character dots</code><dd>
Defines a character as a space and also defines the dot pattern as
such. for example:
<pre class="example"> space \s 0 \s is the escape sequence for blank; 0 means no dots.
</pre>
<p><a name="index-punctuation-7"></a><a name="punctuation-opcode"></a><br><dt><code>punctuation character dots</code><dd>
Associates a punctuation mark in the particular language with a
braille representation and defines the character and dot pattern as
punctuation. For example:
<pre class="example"> punctuation . 46 dot pattern for period in NAB computer braille
</pre>
<p><a name="index-digit-8"></a><a name="digit-opcode"></a><br><dt><code>digit character dots</code><dd>
Associates a digit with a dot pattern and defines the character as a
digit. For example:
<pre class="example"> digit 0 356 NAB computer braille
</pre>
<p><a name="index-uplow-9"></a><a name="uplow-opcode"></a><br><dt><code>uplow characters dots [,dots]</code><dd>
The characters operand must be a pair of letters, of which the first
is uppercase and the second lowercase. The first dots suboperand
indicates the dot pattern for the upper-case letter. It may have more
than one cell. The second dots suboperand must be separated from the
first by a comma and is optional, as indicated by the square brackets.
If present, it indicates the dot pattern for the lower-case letter. It
may also have more than one cell. If the second dots suboperand is not
present the first is used for the lower-case letter as well as the
upper-case letter. This opcode is needed because not all languages
follow a consistent pattern in assigning Unicode codes to upper and
lower case letters. It should be used even for languages that do. The
distinction is important in the forward translator. for example:
<pre class="example"> uplow Aa 17,1
</pre>
<p><a name="index-grouping-10"></a><a name="grouping-opcode"></a><br><dt><code>grouping name characters dots ,dots</code><dd>
This opcode is used to indicate pairs of grouping symbols used in
processing mathematical expressions. These symbols are usually
generated by the MathML interpreter in liblouisxml. They are used in
multipass opcodes. The name operand must contain only letters, but
they may be upper- or lower-case. The characters operand must contain
exactly two Unicode characters. The dots operand must contain exactly
two braille cells, separated by a comma. Note that grouping dot
patterns also need to be declared with the <code>exactdots</code> opcode (see <a href="#exactdots-opcode">exactdots</a>). The
characters may need to be declared with the <code>math</code> opcode (see <a href="#math-opcode">math</a>).
<pre class="example"> grouping mrow \x0001\x0002 1e,2e
grouping mfrac \x0003\x0004 3e,4e
</pre>
<p><a name="index-letter-11"></a><a name="letter-opcode"></a><br><dt><code>letter character dots</code><dd>
Associates a letter in the language with a braille representation and
defines the character as a letter. This is intended for letters which
are neither uppercase nor lowercase.
<p><a name="index-lowercase-12"></a><a name="lowercase-opcode"></a><br><dt><code>lowercase character dots</code><dd>
Associates a character with a dot pattern and defines the character as
a lowercase letter. Both the character and the dot pattern have the
attributes lowercase and letter.
<p><a name="index-uppercase-13"></a><a name="uppercase-opcode"></a><br><dt><code>uppercase character dots</code><dd>
Associates a character with a dot pattern and defines the character as
an uppercase letter. Both the character and the dot pattern have the
attributes uppercase and letter. <code>lowercase</code> and <code>uppercase</code>
should be used when a letter has only one case. Otherwise use the
<code>uplow</code> opcode (see <a href="#uplow-opcode">uplow</a>).
<p><a name="index-litdigit-14"></a><a name="litdigit-opcode"></a><br><dt><code>litdigit digit dots</code><dd>
Associates a digit with the dot pattern which should be used to
represent it in literary texts. For example:
<pre class="example"> litdigit 0 245
litdigit 1 1
</pre>
<p><a name="index-sign-15"></a><a name="sign-opcode"></a><br><dt><code>sign character dots</code><dd>
Associates a character with a dot pattern and defines both as a sign.
This opcode should be used for things like at sign (‘<samp><span class="samp">@</span></samp>’),
percent (‘<samp><span class="samp">%</span></samp>’), dollar sign (‘<samp><span class="samp">$</span></samp>’), etc. Do not use it to
define ordinary punctuation such as period and comma. For example:
<pre class="example"> sign % 4-25-1234 literary percent sign
</pre>
<p><a name="index-math-16"></a><a name="math-opcode"></a><br><dt><code>math character dots</code><dd>
Associates a character and a dot pattern and defines them as a
mathematical symbol. It should be used for less than (‘<samp><span class="samp"><</span></samp>’),
greater than(‘<samp><span class="samp">></span></samp>’), equals(‘<samp><span class="samp">=</span></samp>’), plus(‘<samp><span class="samp">+</span></samp>’), etc. For
example:
<pre class="example"> math + 346 plus
</pre>
</dl>
<p><a name="Braille-Indicator-Opcodes"></a>
<h3 class="section">3.3 Braille Indicator Opcodes</h3>
<p>Braille indicators are dot patterns which are inserted into the
braille text to indicate such things as capitalization, italic type,
computer braille, etc. The opcodes which define them are followed only
by a dot pattern, which may be one or more cells.
<a name="index-capsign-17"></a>
<dl><a name="capsign-opcode"></a><dt><code>capsign dots</code><dd>
The dot pattern which indicates capitalization of a single letter. In
English, this is dot 6. For example:
<pre class="example"> capsign 6
</pre>
<p><a name="index-begcaps-18"></a><a name="begcaps-opcode"></a><br><dt><code>begcaps dots</code><dd>
The dot pattern which begins a block of capital letters. For example:
<pre class="example"> begcaps 6-6
</pre>
<p><a name="index-endcaps-19"></a><a name="endcaps-opcode"></a><br><dt><code>endcaps dots</code><dd>
The dot pattern which ends a block of capital letters within a word.
For example:
<pre class="example"> endcaps 6-3
</pre>
<p><a name="index-letsign-20"></a><a name="letsign-opcode"></a><br><dt><code>letsign dots</code><dd>
This indicator is needed in Grade 2 to show that a single letter is
not a contraction. It is also used when an abbreviation happens to be
a sequence of letters that is the same as a contraction. For example:
<pre class="example"> letsign 56
</pre>
<p><a name="index-noletsign-21"></a><a name="noletsign-opcode"></a><br><dt><code>noletsign letters</code><dd>
<p>The letters in the operand will not be proceeded by a letter sign.
More than one <code>noletsign</code> opcode can be used. This is equivalent
to a single entry containing all the letters. In addition, if a single
letter, such as ‘<samp><span class="samp">a</span></samp>’ in English, is defined as a <code>word</code>
(see <a href="#word-opcode">word</a>) or <code>largesign</code>
(see <a href="#largesign-opcode">largesign</a>), it will be
treated as though it had also been specified in a <code>noletsign</code>
entry.
<p><a name="index-noletsignbefore-22"></a><a name="noletsignbefore-opcode"></a><br><dt><code>noletsignbefore characters</code><dd>
If any of the characters proceeds a single letter without a space a
letter sign is not used. By default the characters apostrophe
(‘<samp><span class="samp">'</span></samp>’) and period (‘<samp><span class="samp">.</span></samp>’) have this property. Use of a
<code>noletsignbefore</code> entry cancels the defaults. If more than one
<code>noletsignbefore</code> entry is used, the characters in all entries
are combined.
<p><a name="index-noletsignafter-23"></a><a name="noletsignafter-opcode"></a><br><dt><code>noletsignafter characters</code><dd>
If any of the characters follows a single letter without a space a
letter sign is not used. By default the characters apostrophe
(‘<samp><span class="samp">'</span></samp>’) and period (‘<samp><span class="samp">.</span></samp>’) have this property. Use of a
<code>noletsignafter</code> entry cancels the defaults. If more than one
<code>noletsignafter</code> entry is used the characters in all entries are
combined.
<p><a name="index-numsign-24"></a><a name="numsign-opcode"></a><br><dt><code>numsign dots</code><dd>
The translator inserts this indicator before numbers made up of digits
defined with the <code>litdigit</code> opcode (see <a href="#litdigit-opcode">litdigit</a>) to show that they are a number
and not letters or some other symbols. For example:
<pre class="example"> numsign 3456
</pre>
</dl>
<p><a name="Emphasis-Opcodes"></a>
<h3 class="section">3.4 Emphasis Opcodes</h3>
<p>These also define braille indicators, but they require more
explanation. There are four sets, for italic, bold, underline and
computer braille. In each of the first three sets there are seven
opcodes, for use before the first word of a phrase, for use before the
last word, for use after the last word, for use before the first
letter (or character) if emphasis starts in the middle of a word, for
use after the last letter (or character) if emphasis ends in the
middle of a word, before a single letter (or character), and to
specify the length of a phrase to which the first-word and
last-word-before indicators apply. This rather elaborate set of
emphasis opcodes was devised to try to meet all contingencies. It is
unlikely that a translation table will contain all of them. The
translator checks for their presence. If they are present, it first
looks to see if the single-letter indicator should be used. Then it
looks at the word (or phrase) indicators and finally at the
multi-letter indicators.
<p>The translator will apply up to two emphasis indicators to each phrase
or string of characters, depending on what the <code>typeform</code>
parameter in its calling sequence indicates (see <a href="#Programming-with-liblouis">Programming with liblouis</a>).
<p>For computer braille there are only two braille indicators, for the
beginning and end of a sequence of characters to be rendered in
computer braille. Such a sequence may also have other emphasis. The
computer braille indicators are applied not only when computer braille
is indicated in the <code>typeform</code> parameter, but also when a
sequence of characters is determined to be computer braille because it
contains a subsequence defined by the <code>compbrl</code> opcode (see <a href="#compbrl-opcode">compbrl</a>) or the
<code>literal</code> opcode (see <a href="#literal-opcode">literal</a>).
<p>Here are the various emphasis opcodes.
<a name="index-firstwordital-25"></a>
<dl><a name="firstwordital-opcode"></a><dt><code>firstwordital dots</code><dd>
This is the braille indicator to be placed before the first word of an
italicized phrase that is longer than the value given in the
<code>lenitalphrase</code> opcode (see <a href="#lenitalphrase-opcode">lenitalphrase</a>). For example:
<pre class="example"> firstwordital 46-46 English indicator
</pre>
<p><a name="index-lastworditalbefore-26"></a><a name="lastworditalbefore-opcode"></a><br><dt><code>lastworditalbefore dots</code><dd>
This is the braille indicator to be placed before the last word of an
italicized phrase. In addition, if <code>firstwordital</code> is not used,
this braille indicator is doubled and placed before the first word. Do
not use <code>lastworditalbefore</code> and <code>lastworditalafter</code> in the
same table. For example:
<pre class="example"> lastworditalbefore 4-6
</pre>
<p><a name="index-lastworditalafter-27"></a><a name="lastworditalafter-opcode"></a><br><dt><code>lastworditalafter dots</code><dd>
This is the braille indicator to be placed after the last word of an
italicized phrase. Do not use <code>lastworditalbefore</code> and
<code>lastworditalafter</code> in the same table. See also the
<code>lenitalphrase</code> opcode (see <a href="#lenitalphrase-opcode">lenitalphrase</a>) for more information.
<p><a name="index-firstletterital-28"></a><a name="firstletterital-opcode"></a><br><dt><code>firstletterital dots</code><dd>
This is the braille indicator to be placed before the first letter (or
character) if italicization begins in the middle of a word.
<p><a name="index-lastletterital-29"></a><a name="lastletterital-opcode"></a><br><dt><code>lastletterital dots</code><dd>
This is the braille indicator to be placed after the last letter (or
character) when italicization ends in the middle of a word.
<p><a name="index-singleletterital-30"></a><a name="singleletterital-opcode"></a><br><dt><code>singleletterital dots</code><dd>
This braille indicator is used if only a single letter (or character)
is italicized.
<p><a name="index-lenitalphrase-31"></a><a name="lenitalphrase-opcode"></a><br><dt><code>lenitalphrase number</code><dd>
If <code>lastworditalbefore</code> is used, an italicized phrase is checked
to see how many words it contains. If this number is less than or
equal to the number given in the <code>lenitalphrase</code> opcode, the
<code>lastworditalbefore</code> sign is placed in front of each word. If it
is greater, the <code>firstwordital</code> indicator is placed before the
first word and the <code>lastworditalbefore</code> indicator is placed after
the last word. Note that if the <code>firstwordital</code> opcode is not
used its indicator is made up by doubling the dot pattern given in the
<code>lastworditalbefore</code> entry. For example:
<pre class="example"> lenitalphrase 4
</pre>
<p><a name="index-firstwordbold-32"></a><a name="firstwordbold-opcode"></a><br><dt><code>firstwordbold dots</code><dd>
This is the braille indicator to be placed before the first word of a
bold phrase. For example:
<pre class="example"> firstwordbold 456-456
</pre>
<p><a name="index-lastwordboldbefore-33"></a><a name="lastwordboldbefore-opcode"></a><br><dt><code>lastwordboldbefore dots</code><dd>
This is the braille indicator to be placed before the last word of a
bold phrase. In addition, if <code>firstwordbold</code> is not used, this
braille indicator is doubled and placed before the first word. Do not
use <code>lastwordboldbefore</code> and <code>lastwordboldafter</code> in the same
table. For example:
<pre class="example"> lastwordboldbefore 456
</pre>
<p><a name="index-lastwordboldafter-34"></a><a name="lastwordboldafter-opcode"></a><br><dt><code>lastwordboldafter dots</code><dd>
This is the braille indicator to be placed after the last word of a
bold phrase. Do not use <code>lastwordboldbefore</code> and
<code>lastwordboldafter</code> in the same table.
<p><a name="index-firstletterbold-35"></a><a name="firstletterbold-opcode"></a><br><dt><code>firstletterbold dots</code><dd>
This is the braille indicator to be placed before the first letter (or
character) if bold emphasis begins in the middle of a word.
<p><a name="index-lastletterbold-36"></a><a name="lastletterbold-opcode"></a><br><dt><code>lastletterbold dots</code><dd>
This is the braille indicator to be placed after the last letter (or
character) when bold emphasis ends in the middle of a word.
<p><a name="index-singleletterbold-37"></a><a name="singleletterbold-opcode"></a><br><dt><code>singleletterbold dots</code><dd>
This braille indicator is used if only a single letter (or character)
is in boldface.
<p><a name="index-lenboldphrase-38"></a><a name="lenboldphrase-opcode"></a><br><dt><code>lenboldphrase number</code><dd>
If <code>lastwordboldbefore</code> is used, a bold phrase is checked to see
how many words it contains. If this number is less than or equal to
the number given in the <code>lenboldphrase</code> opcode, the
<code>lastwordboldbefore</code> sign is placed in front of each word. If it
is greater, the <code>firstwordbold</code> indicator is placed before the
first word and the <code>lastwordboldbefore</code> indicator is placed after
the last word. Note that if the <code>firstwordbold</code> opcode is not
used its indicator is made up by doubling the dot pattern given in the
<code>lastwordboldbefore</code> entry.
<p><a name="index-firstwordunder-39"></a><a name="firstwordunder-opcode"></a><br><dt><code>firstwordunder dots</code><dd>
This is the braille indicator to be placed before the first word of an
underlined phrase.
<p><a name="index-lastwordunderbefore-40"></a><a name="lastwordunderbefore-opcode"></a><br><dt><code>lastwordunderbefore dots</code><dd>
This is the braille indicator to be placed before the last word of an
underlined phrase. In addition, if <code>firstwordunder</code> is not used,
this braille indicator is doubled and placed before the first word.
<p><a name="index-lastwordunderafter-41"></a><a name="lastwordunderafter-opcode"></a><br><dt><code>lastwordunderafter dots</code><dd>
This is the braille indicator to be placed after the last word of an
underlined phrase.
<p><a name="index-firstletterunder-42"></a><a name="firstletterunder-opcode"></a><br><dt><code>firstletterunder dots</code><dd>
This is the braille indicator to be placed before the first letter (or
character) if underline emphasis begins in the middle of a word.
<p><a name="index-lastletterunder-43"></a><a name="lastletterunder-opcode"></a><br><dt><code>lastletterunder dots</code><dd>
This is the braille indicator to be placed after the last letter (or
character) when underline emphasis ends in the middle of a word.
<p><a name="index-singleletterunder-44"></a><a name="singleletterunder-opcode"></a><br><dt><code>singleletterunder dots</code><dd>
This braille indicator is used if only a single letter (or character)
is underlined.
<p><a name="index-lenunderphrase-45"></a><a name="lenunderphrase-opcode"></a><br><dt><code>lenunderphrase number</code><dd>
If <code>lastwordunderbefore</code> is used, an underlined phrase is checked
to see how many words it contains. If this number is less than or
equal to the number given in the <code>lenunderphrase</code> opcode, the
<code>lastwordunderbefore</code> sign is placed in front of each word. If it
is greater, the <code>firstwordunder</code> indicator is placed before the
first word and the <code>lastwordunderbefore</code> indicator is placed
after the last word. Note that if the <code>firstwordunder</code> opcode is
not used its indicator is made up by doubling the dot pattern given in
the <code>lastwordunderbefore</code> entry.
<p><a name="index-begcomp-46"></a><a name="begcomp-opcode"></a><br><dt><code>begcomp dots</code><dd>
This braille indicator is placed before a sequence of characters
translated in computer braille, whether this sequence is indicated in
the <code>typeform</code> parameter (see <a href="#Programming-with-liblouis">Programming with liblouis</a>) or
inferred because it contains a subsequence specified by the
<code>compbrl</code> opcode (see <a href="#compbrl-opcode">compbrl</a>).
<p><a name="index-endcomp-47"></a><a name="endcomp-opcode"></a><br><dt><code>endcomp dots</code><dd>
This braille indicator is placed after a sequence of characters
translated in computer braille, whether this sequence is indicated in
the <code>typeform</code> parameter (see <a href="#Programming-with-liblouis">Programming with liblouis</a>) or
inferred because it contains a subsequence specified by the
<code>compbrl</code> opcode (see <a href="#compbrl-opcode">compbrl</a>).
</dl>
<p><a name="Special-Symbol-Opcodes"></a>
<h3 class="section">3.5 Special Symbol Opcodes</h3>
<p>These opcodes define certain symbols, such as the decimal point, which
require special treatment.
<a name="index-decpoint-48"></a>
<dl><a name="decpoint-opcode"></a><dt><code>decpoint character dots</code><dd>
This opcode defines the decimal point. The character operand must have
only one character. For example, in <samp><span class="file">en-us-g1.ctb</span></samp> we have:
<pre class="example"> decpoint . 46
</pre>
<p><a name="index-hyphen-49"></a><a name="hyphen-opcode"></a><br><dt><code>hyphen character dots</code><dd>
This opcode defines the hyphen, that is, the character used in
compound words such as have-nots. The back-translator uses it to
determine the end of individual words.
</dl>
<p><a name="Special-Processing-Opcodes"></a>
<h3 class="section">3.6 Special Processing Opcodes</h3>
<p>These opcodes cause special processing to be carried out.
<a name="index-capsnocont-50"></a>
<dl><a name="capsnocont-opcode"></a><dt><code>capsnocont</code><dd>
This opcode has no operands. If it is specified, words or parts of
words in all caps are not contracted. This is needed for languages
such as Norwegian.
</dl>
<p><a name="Translation-Opcodes"></a>
<h3 class="section">3.7 Translation Opcodes</h3>
<p>These opcodes define the braille representations for character
sequences. Each of them defines an entry within the contraction table.
These entries may be defined in any order except, as noted below, when
they define alternate representations for the same character sequence.
<p>Each of these opcodes specifies a condition under which the
translation is legal, and each also has a characters operand and a
dots operand. The text being translated is processed strictly from
left to right, character by character, with the most eligible entry
for each position being used. If there is more than one eligible entry
for a given position in the text, then the one with the longest
character string is used. If there is more than one eligible entry for
the same character string, then the one defined first is is tested for
legality first. (This is the only case in which the order of the
entries makes a difference.)
<p>The characters operand is a sequence or string of characters preceded
and followed by whitespace. Each character can be entered in the
normal way, or it can be defined as a four-digit hexadecimal number
preceded by ‘<samp><span class="samp">\x</span></samp>’.
<p>The dots operand defines the braille representation for the characters
operand. It may also be specified as an equals sign (‘<samp><span class="samp">=</span></samp>’). This
means that the the default representation for each character
(see <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a>) within the sequence is to be
used.
<p>In what follows the word ‘<samp><span class="samp">characters</span></samp>’ means a sequence of one or
more consecutive letters between spaces and/or punctuation marks.
<a name="index-noback-51"></a>
<dl><a name="noback-opcode"></a><dt><code>noback opcode ...</code><dd>
This is an opcode prefix, that is to say, it modifies the operation of
the opcode that follows it on the same line. noback specifies that no
back-translation is to be done using this line.
<pre class="example"> noback always ;\s; 0
</pre>
<p><a name="index-nofor-52"></a><a name="nofor-opcode"></a><br><dt><code>nofor opcode ...</code><dd>
This is an opcode prefix which modifies the operation of the opcode
following it on the same line. nofor specifies that forward translation
is not to use the information on this line.
<p><a name="index-compbrl-53"></a><a name="compbrl-opcode"></a><br><dt><code>compbrl characters</code><dd>
If the characters are found within a block of text surrounded by
whitespace the entire block is translated according to the default
braille representations defined by the <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a>, if 8-dot computer braille is enabled or according to the dot
patterns given in the <code>comp6</code> opcode (see <a href="#comp6-opcode">comp6</a>), if 6-dot computer braille is
enabled. For example:
<pre class="example"> compbrl www translate URLs in computer braille
</pre>
<p><a name="index-comp6-54"></a><a name="comp6-opcode"></a><br><dt><code>comp6 character dots</code><dd>
This opcode specifies the translation of characters in 6-dot computer
braille. It is necessary because the translation of a single character
may require more than one cell. The first operand must be a character
with a decimal representation from 0 to 255 inclusive. The second
operand may specify as many cells as necessary. The opcode is somewhat
of a misnomer, since any dots, not just dots 1 through 6, can be
specified. This even includes virtual dots.
<p><a name="index-nocont-55"></a><a name="nocont-opcode"></a><br><dt><code>nocont characters</code><dd>
Like <code>compbrl</code>, except that the string is uncontracted.
<code>prepunc</code> opcode (see <a href="#prepunc-opcode">prepunc</a>) and <code>postpunc</code> opcode (see <a href="#postpunc-opcode">postpunc</a>) rules are applied,
however. This is useful for specifying that foreign words should not
be contracted in an entire document.
<p><a name="index-replace-56"></a><a name="replace-opcode"></a><br><dt><code>replace characters {characters}</code><dd>
Replace the first set of characters, no matter where they appear, with
the second. Note that the second operand is <em>NOT</em> a dot pattern.
It is also optional. If it is omitted the character(s) in the first
operand will be discarded. This is useful for ignoring characters. It
is possible that the "ignored" characters may still affect the
translation indirectly. Therefore, it is preferable to use
<code>correct</code> opcode (see <a href="#correct-opcode">correct</a>).
<p><a name="index-always-57"></a><a name="always-opcode"></a><br><dt><code>always characters dots</code><dd>
Replace the characters with the dot pattern no matter where they
appear. Do <em>NOT</em> use an entry such as <code>always a 1</code>. Use the
<code>uplow</code>, <code>letter</code>, etc. character definition opcodes
instead. For example:
<pre class="example"> always world 456-2456 unconditional translation
</pre>
<p><a name="index-repeated-58"></a><a name="repeated-opcode"></a><br><dt><code>repeated characters dots</code><dd>
Replace the characters with the dot pattern no matter where they
appear. Ignore any consecutive repetitions of the same character
sequence. This is useful for shortening long strings of spaces or
hyphens or periods. For example:
<pre class="example"> repeated --- 36-36-36 shorten separator lines made with hyphens
</pre>
<p><a name="index-repword-59"></a><a name="repword-opcode"></a><br><dt><code>repword characters dots</code><dd>
When characters are encountered check to see if the word before this
string matches the word after it. If so, replace characters with dots
and eliminate the second word and any word following another occurrence
of characters that is the same. This opcode is used in Malaysian
braille. In this case the rule is:
<pre class="example"> repword - 123456
</pre>
<p><a name="index-largesign-60"></a><a name="largesign-opcode"></a><br><dt><code>largesign characters dots</code><dd>
Replace the characters with the dot pattern no matter where they
appear. In addition, if two words defined as large signs follow each
other, remove the space between them. For example, in
<samp><span class="file">en-us-g2.ctb</span></samp> the words ‘<samp><span class="samp">and</span></samp>’ and ‘<samp><span class="samp">the</span></samp>’ are both
defined as large signs. Thus, in the phrase ‘<samp><span class="samp">the cat and the dog</span></samp>’
the space would be deleted between ‘<samp><span class="samp">and</span></samp>’ and ‘<samp><span class="samp">the</span></samp>’, with the
result ‘<samp><span class="samp">the cat andthe dog</span></samp>’. Of course, ‘<samp><span class="samp">and</span></samp>’ and ‘<samp><span class="samp">the</span></samp>’
would be properly contracted. The term <code>largesign</code> is a bit of
braille jargon that pleases braille experts.
<p><a name="index-word-61"></a><a name="word-opcode"></a><br><dt><code>word characters dots</code><dd>
Replace the characters with the dot pattern if they are a word, that
is, are surrounded by whitespace and/or punctuation.
<p><a name="index-syllable-62"></a><a name="syllable-opcode"></a><br><dt><code>syllable characters dots</code><dd>
As its name indicates, this opcode defines a "syllable" which must be
represented by exactly the dot patterns given. Contractions may not
cross the boundaries of this "syllable" either from left or right. The
character string defined by this opcode need not be a lexical
syllable, though it usually will be. The equal sign in the following
example means that the the default representation for each character
within the sequence is to be used (see <a href="#Translation-Opcodes">Translation Opcodes</a>):
<pre class="example"> syllable horse = sawhorse, horseradish
</pre>
<p><a name="index-nocross-63"></a><a name="nocross-opcode"></a><br><dt><code>nocross characters dots</code><dd>
Replace the characters with the dot pattern if the characters are all
in one syllable (do not cross a syllable boundary). For this opcode to
work, a hyphenation table must be included. If this is not done,
<code>nocross</code> behaves like the <code>always</code> opcode (see <a href="#always-opcode">always</a>). For example, if
the English Grade 2 table is being used and the appropriate
hyphenation table has been included <code>nocross sh 146</code> will cause
the ‘<samp><span class="samp">sh</span></samp>’ in ‘<samp><span class="samp">monkshood</span></samp>’ not to be contracted.
<p><a name="index-joinword-64"></a><a name="joinword-opcode"></a><br><dt><code>joinword characters dots</code><dd>
Replace the characters with the dot pattern if they are a word which
is followed by whitespace and a letter. In addition remove the
whitespace. For example, <samp><span class="file">en-us-g2.ctb</span></samp> has <code>joinword to
235</code>. This means that if the word ‘<samp><span class="samp">to</span></samp>’ is followed by another
word the contraction is to be used and the space is to be omitted. If
these conditions are not met, the word is translated according to any
other opcodes that may apply to it.
<p><a name="index-lowword-65"></a><a name="lowword-opcode"></a><br><dt><code>lowword characters dots</code><dd>
Replace the characters with the dot pattern if they are a word
preceded and followed by whitespace. No punctuation either before or
after the word is allowed. The term <code>lowword</code> derives from the
fact that in English these contractions are written in the lower part
of the cell. For example:
<pre class="example"> lowword were 2356
</pre>
<p><a name="index-contraction-66"></a><a name="contraction-opcode"></a><br><dt><code>contraction characters</code><dd>
If you look at <samp><span class="file">en-us-g2.ctb</span></samp> you will see that some words are
actually contracted into some of their own letters. A famous example
among braille transcribers is ‘<samp><span class="samp">also</span></samp>’, which is contracted as
‘<samp><span class="samp">al</span></samp>’. But this is also the name of a person. To take another
example, ‘<samp><span class="samp">altogether</span></samp>’ is contracted as ‘<samp><span class="samp">alt</span></samp>’, but this is
the abbreviation for the alternate key on a computer keyboard.
Similarly ‘<samp><span class="samp">could</span></samp>’ is contracted into ‘<samp><span class="samp">cd</span></samp>’, but this is the
abbreviation for compact disk. To prevent confusion in such cases, the
letter sign (see <code>letsign</code> opcode (see <a href="#letsign-opcode">letsign</a>)) is placed before such letter
combinations when they actually are abbreviations, not contractions.
The <code>contraction</code> opcode tells the translator to do this.
<p><a name="index-sufword-67"></a><a name="sufword-opcode"></a><br><dt><code>sufword characters dots</code><dd>
Replace the characters with the dot pattern if they are either a word
or at the beginning of a word.
<p><a name="index-prfword-68"></a><a name="prfword-opcode"></a><br><dt><code>prfword characters dots</code><dd>
Replace the characters with the dot pattern if they are either a word
or at the end of a word.
<p><a name="index-begword-69"></a><a name="begword-opcode"></a><br><dt><code>begword characters dots</code><dd>
Replace the characters with the dot pattern if they are at the
beginning of a word.
<p><a name="index-begmidword-70"></a><a name="begmidword-opcode"></a><br><dt><code>begmidword characters dots</code><dd>
Replace the characters with the dot pattern if they are either at the
beginning or in the middle of a word.
<p><a name="index-midword-71"></a><a name="midword-opcode"></a><br><dt><code>midword characters dots</code><dd>
Replace the characters with the dot pattern if they are in the middle
of a word.
<p><a name="index-midendword-72"></a><a name="midendword-opcode"></a><br><dt><code>midendword characters dots</code><dd>
Replace the characters with the dot pattern if they are either in the
middle or at the end of a word.
<p><a name="index-endword-73"></a><a name="endword-opcode"></a><br><dt><code>endword characters dots</code><dd>
Replace the characters with the dot pattern if they are at the end of
a word.
<p><a name="index-partword-74"></a><a name="partword-opcode"></a><br><dt><code>partword characters dots</code><dd>
Replace the characters with the dot pattern if the characters are
anywhere in a word, that is, if they are proceeded or followed by a
letter.
<p><a name="index-exactdots-75"></a><a name="exactdots-opcode"></a><br><dt><code>exactdots @dots</code><dd>
Note that the operand must begin with an at sign (‘<samp><span class="samp">@</span></samp>’). The dot
pattern following it is evaluated for validity. If it is valid,
whenever an at sign followed by this dot pattern appears in the source
document it is replaced by the characters corresponding to the dot
pattern in the output. This opcode is intended for use in liblouisxml
semantic-action files to specify exact dot patterns, as in
mathematical codes. For example:
<pre class="example"> exactdots @4-46-12356
</pre>
<p>will produce the characters with these dot patterns in the output.
<p><a name="index-prepunc-76"></a><a name="prepunc-opcode"></a><br><dt><code>prepunc characters dots</code><dd>
Replace the characters with the dot pattern if they are part of
punctuation at the beginning of a word.
<p><a name="index-postpunc-77"></a><a name="postpunc-opcode"></a><br><dt><code>postpunc characters dots</code><dd>
Replace the characters with the dot pattern if they are part of
punctuation at the end of a word.
<p><a name="index-begnum-78"></a><a name="begnum-opcode"></a><br><dt><code>begnum characters dots</code><dd>
Replace the characters with the dot pattern if they are at the
beginning of a number, that is, before all its digits. For example, in
<samp><span class="file">en-us-g1.ctb</span></samp> we have <code>begnum # 4</code>.
<p><a name="index-midnum-79"></a><a name="midnum-opcode"></a><br><dt><code>midnum characters dots</code><dd>
Replace the characters with the dot pattern if they are in the middle
of a number. For example, <samp><span class="file">en-us-g1.ctb</span></samp> has <code>midnum . 46</code>.
This is because the decimal point has a different dot pattern than the
period.
<p><a name="index-endnum-80"></a><a name="endnum-opcode"></a><br><dt><code>endnum characters dots</code><dd>
Replace the characters with the dot pattern if they are at the end of
a number. For example <samp><span class="file">en-us-g1.ctb</span></samp> has <code>endnum th 1456</code>.
This handles things like ‘<samp><span class="samp">4th</span></samp>’. A letter sign is <em>NOT</em>
inserted.
<p><a name="index-joinnum-81"></a><a name="joinnum-opcode"></a><br><dt><code>joinnum characters dots</code><dd>
Replace the characters with the dot pattern. In addition, if
whitespace and a number follows omit the whitespace. This opcode can
be used to join currency symbols to numbers for example:
<pre class="example"> joinnum \x20AC 15 (EURO SIGN)
joinnum \x0024 145 (DOLLAR SIGN)
joinnum \x00A3 1234 (POUND SIGN)
joinnum \x00A5 13456 (YEN SIGN)
</pre>
</dl>
<p><a name="Character-Class-Opcodes"></a>
<a name="Character_002dClass-Opcodes"></a>
<h3 class="section">3.8 Character-Class Opcodes</h3>
<p>These opcodes define and use character classes. A character class
associates a set of characters with a name. The name then refers to
any character within the class. A character may belong to more than
one class.
<p>The basic character classes correspond to the character definition
opcodes, with the exception of the <code>uplow</code> opcode (see <a href="#uplow-opcode">uplow</a>), which defines
characters belonging to the two classes <code>uppercase</code> and
<code>lowercase</code>. These classes are:
<dl>
<dt><code>space</code><dd>Whitespace characters such as blank and tab
<br><dt><code>digit</code><dd>Numeric characters
<br><dt><code>letter</code><dd>Both uppercase and lowercase alphabetic characters
<br><dt><code>lowercase</code><dd>Lowercase alphabetic characters
<br><dt><code>uppercase</code><dd>Uppercase alphabetic characters
<br><dt><code>punctuation</code><dd>Punctuation marks
<br><dt><code>sign</code><dd>Signs such as percent (‘<samp><span class="samp">%</span></samp>’)
<br><dt><code>math</code><dd>Mathematical symbols
<br><dt><code>litdigit</code><dd>Literary digit
<br><dt><code>undefined</code><dd>Not properly defined
</dl>
<p>The opcodes which define and use character classes are shown below.
For examples see <samp><span class="file">fr-abrege.ctb</span></samp>.
<a name="index-class-82"></a>
<dl><a name="class-opcode"></a><dt><code>class name characters</code><dd>
Define a new character class. The characters operand must be specified
as a string. A character class may not be used until it has been
defined.
<p><a name="index-after-83"></a><a name="after-opcode"></a><br><dt><code>after class opcode ...</code><dd>
The specified opcode is further constrained in that the matched
character sequence must be immediately preceded by a character
belonging to the specified class. If this opcode is used more than
once on the same line then the union of the characters in all the
classes is used.
<p><a name="index-before-84"></a><a name="before-opcode"></a><br><dt><code>before class opcode ...</code><dd>
The specified opcode is further constrained in that the matched
character sequence must be immediately followed by a character
belonging to the specified class. If this opcode is used more than
once on the same line then the union of the characters in all the
classes is used.
</dl>
<p><a name="Swap-Opcodes"></a>
<h3 class="section">3.9 Swap Opcodes</h3>
<p>The swap opcodes are needed to tell the <code>context</code> opcode (see <a href="#context-opcode">context</a>), the
<code>correct</code> opcode (see <a href="#correct-opcode">correct</a>) and multipass opcodes which dot patterns to swap
for which characters. There are three, <code>swapcd</code>, <code>swapdd</code>
and <code>swapcc</code>. The first swaps dot patterns for characters. The
second swaps dot patterns for dot patterns and the third swaps
characters for characters. The first is used in the <code>context</code>
opcode and the second is used in the multipass opcodes. Dot patterns
are separated by commas and may contain more than one cell.
<a name="index-swapcd-85"></a>
<dl><a name="swapcd-opcode"></a><dt><code>swapcd name characters dots, dots, dots, ...</code><dd>
See above paragraph for explanation. For example:
<pre class="example"> swapcd dropped 0123456789 356,2,23,...
</pre>
<p><a name="index-swapdd-86"></a><a name="swapdd-opcode"></a><br><dt><code>swapdd name dots, dots, dots ... dotpattern1, dotpattern2, dotpattern3, ...</code><dd>
The <code>swapdd</code> opcode defines substitutions for the multipass
opcodes. In the second operand the dot patterns must be single cells,
but in the third operand multi-cell dot patterns are allowed. This is
because multi-cell patterns in the second operand would lead to
ambiguities.
<p><a name="index-swapcc-87"></a><a name="swapcc-opcode"></a><br><dt><code>swapcc name characters characters</code><dd>
The <code>swapcc</code> opcode swaps characters in its second operand for
characters in the corresponding places in its third operand. It is
intended for use with <code>correct</code> opcodes and can solve problems
such as formatting phone numbers.
</dl>
<p><a name="The-Context-and-Multipass-Opcodes"></a>
<h3 class="section">3.10 The Context and Multipass Opcodes</h3>
<p>The <code>context</code> and multipass opcodes (<code>pass2</code>, <code>pass3</code>
and <code>pass4</code>) provide translation capabilities beyond those of the
basic translation opcodes (see <a href="#Translation-Opcodes">Translation Opcodes</a>) discussed
previously. The multipass opcodes cause additional passes to be made
over the string to be translated. The number after the word
<code>pass</code> indicates in which pass the entry is to be applied. If no
multipass opcodes are given, only the first translation pass is made.
The <code>context</code> opcode is basically a multipass opcode for the
first pass. It differs slightly from the multipass opcodes per se. The
format of all these opcodes is <code>opcode test action</code>. The specific
opcodes are invoked as follows:
<dl>
<a name="context-opcode"></a><a name="index-context-88"></a><a name="index-pass2-89"></a><a name="index-pass3-90"></a><a name="index-pass4-91"></a><dt><code>context test action</code><dt><code>pass2 test action</code><dt><code>pass3 test action</code><dt><code>pass4 test action</code><dd></dl>
<p>The <code>test</code> and <code>action</code> operands have suboperands. Each
suboperand begins with a non-alphanumeric character and ends when
another non-alphanumeric character is encountered. The suboperands and
their initial characters are as follows.
<dl>
<dt><kbd>" (double quote)</kbd><dd>a string of characters. This string must be terminated by another
double quote. It may contain any characters. If a double quote is
needed within the string, it must be preceded by a backslash
(‘<samp><span class="samp">\</span></samp>’). If a space is needed, it must be represented by the escape
sequence \s. This suboperand is valid only in the test part of the
<code>context</code> opcode.
<br><dt><kbd>@ (at sign)</kbd><dd>a sequence of dot patterns. Cells are separated by hyphens as usual.
This suboperand is not valid in the test part of the context and
correct opcodes.
<br><dt><kbd>` (accent mark)</kbd><dd>If this is the beginning of the string being translated this suboperand
is true. It is valid only in the test part and must be the first thing
in this operand.
<br><dt><kbd>~ (tilde)</kbd><dd>If this is the end of the string being translated this suboperand is
true. It is valid only in the test part and must be the last thing in
this operand.
<br><dt><kbd>$ (dollar sign)</kbd><dd>a string of attributes, such as ‘<samp><span class="samp">d</span></samp>’ for digit, ‘<samp><span class="samp">l</span></samp>’ for
letter, etc. More than one attribute can be given. If you wish to
check characters with any attribute, use the letter ‘<samp><span class="samp">a</span></samp>’. Input
characters are checked to see if they have at least one of the
attributes. The attribute string can be followed by numbers specifying
how many characters are to be checked. If no numbers are given, 1 is
assumed. If two numbers separated by a hyphen are given, the input is
checked to make sure that at least the first number of characters with
the attributes are present, but no more than the second number. If
only one number is present, then exactly that many characters must
have the attributes. A period instead of the numbers indicates an
indefinite number of characters. This suboperand is valid in all test
parts but not in action parts. For the characters which can be used in
attribute strings, see the following table.
<br><dt><kbd>! (exclamation point)</kbd><dd>reverses the logical meaning of the suboperand which follows. For
example, !$d is true only if the character is <em>NOT</em> a digit. This
suboperand is valid in test parts only.
<br><dt><kbd>% (percent sign)</kbd><dd>the name of a class defined by the <code>class</code> opcode (see <a href="#class-opcode">class</a>) or the name of a
swap set defined by the swap opcodes (see <a href="#Swap-Opcodes">Swap Opcodes</a>). Names may
contain only letters. The letters may be upper or
lower-case. The case matters. Class names may be used in test parts
only. Swap names are valid everywhere.
<br><dt><kbd>{ (left brace)</kbd><dd>Name: the name of a grouping pair. The left brace indicates that the
first (or left) member of the pair is to be used in matching. If this is
between replacement brackets it must be the only item. This is also
valid in the action part.
<br><dt><kbd>} (right brace)</kbd><dd>Name: the name of a grouping pair. The right brace indicates that the
second (or right) member is to be used in matching. See the remarks on
the left brace immediately above.
<br><dt><kbd>/ (slash)</kbd><dd>Search the input for the expression following the slash and return true
if found. This can be used to set a variable.
<br><dt><kbd>_ (underscore)</kbd><dd>Move backward. If a number follows, move backward that number of
characters. The program never moves backward beyond the beginning of
the input string. This suboperand is valid only in test parts.
<br><dt><kbd>[ (left bracket)</kbd><dd>start replacement here. This suboperand must always be paired with a
right bracket and is valid only in test parts. Multiple pairs of
square brackets in a single expression are not allowed.
<br><dt><kbd>] (right bracket)</kbd><dd>end replacement here. This suboperand must always be paired with a
left bracket and is valid only in test parts.
<br><dt><kbd># (number sign or crosshatch)</kbd><dd>test or set a variable. Variables are referred to by numbers 1 to 50,
for example, <code>#1</code>, <code>#2</code>, <code>#25</code>. Variables may be set by
one <code>context</code> or multipass opcode and tested by another. Thus, an
operation that occurs at one place in a translation can tell an
operation that occurs later about itself. This feature will be used in
math translation, and it may also help to alleviate the need for new
opcodes. This suboperand is valid everywhere.
<p>Variables are set in the action part. To set a variable use an
expression like <code>#1=1</code>, <code>#2=5</code>, etc. Variables are also
incremented and decremented in the action part with expressions like
<code>#1+</code>, <code>#3-</code>, etc. These operators increment or decrement
the variable by 1.
<p>Variables are tested in the test part with expressions like
<code>#1=2</code>, <code>#3<4</code>, <code>#5>6</code>, etc.
<br><dt><kbd>* (asterisk)</kbd><dd>Copy the characters or dot patterns in the input within the
replacement brackets into the output and discard anything else that
may match. This feature is used, for example, for handling numeric
subscripts in Nemeth. This suboperand is valid only in action parts.
<br><dt><kbd>? (question mark)</kbd><dd>Valid only in the action part. The characters to be replaced are
simply ignored. That is, they are replaced with nothing. If either
member of a grouping pair is in the replace brackets the other member at
the same level is also removed.
</dl>
<p>The characters which can be used in attribute strings are as follows:
<dl>
<dt><kbd>a</kbd><dd>any attribute
<br><dt><kbd>d</kbd><dd>digit
<br><dt><kbd>D</kbd><dd>literary digit
<br><dt><kbd>l</kbd><dd>letter
<br><dt><kbd>m</kbd><dd>math
<br><dt><kbd>p</kbd><dd>punctuation
<br><dt><kbd>S</kbd><dd>sign
<br><dt><kbd>s</kbd><dd>space
<br><dt><kbd>U</kbd><dd>uppercase
<br><dt><kbd>u</kbd><dd>lowercase
<br><dt><kbd>w</kbd><dd>first user-defined class
<br><dt><kbd>x</kbd><dd>second user-defined class
<br><dt><kbd>y</kbd><dd>third user-defined class
<br><dt><kbd>z</kbd><dd>fourth user-defined class
</dl>
<p>The following illustrates the algorithm how text is evaluated with
multipass expressions:
<p class="noindent">Loop over context, pass2, pass3 and pass4 and do the following for each pass:
<ol type=a start=1>
<li>Match the text following the cursor against all expressions in the
current pass
<li>If there is no match: shift the cursor one position to the right and
continue the loop
<li>If there is a match: choose the longest match
<li>Do the replacement (everything between square brackets)
<li>Place the cursor after the replaced text
<li>continue loop
</ol>
<p>Note that if any multipass opcode or the <code>correct</code> opcode (see <a href="#correct-opcode">correct</a>) is used
and the <code>pass1Only</code> mode bit (see <a href="#lou_005ftranslateString">lou_translateString</a>) is not
set, input and output positions may be incorrect.
<p><a name="The-correct-Opcode"></a>
<h3 class="section">3.11 The correct Opcode</h3>
<a name="index-correct-92"></a>
<dl><a name="correct-opcode"></a><dt><code>correct test action</code><dd>
Because some input (such as that from an OCR program) may contain
systematic errors, it is sometimes advantageous to use a
pre-translation pass to remove them. The errors and their corrections
are specified by the <code>correct</code> opcode. If there are no
<code>correct</code> opcodes in a table, the pre-translation pass is not
used. The format of the <code>correct</code> opcode is very similar to that
of the <code>context</code> opcode (see <a href="#context-opcode">context</a>). The only difference is that in the action
part strings may be used and dot patterns may not be used. Some
examples of <code>correct</code> opcode entries are:
<pre class="example"> correct "\\" ? Eliminate backslashes
correct "cornf" "comf" fix a common "scano"
correct "cornm" "comm"
correct "cornp" "comp"
correct "*" ? Get rid of stray asterisks
correct "|" ? ditto for vertical bars
correct "\s?" "?" drop space before question mark
</pre>
<p>Note that if the <code>correct</code> opcode is used and the
<code>pass1Only</code> mode bit (see <a href="#lou_005ftranslateString">lou_translateString</a>) is not set,
input and output positions may be incorrect.
</dl>
<p><a name="Miscellaneous-Opcodes"></a>
<h3 class="section">3.12 Miscellaneous Opcodes</h3>
<a name="index-include-93"></a>
<dl><a name="include-opcode"></a><dt><code>include filename</code><dd>
Read the file indicated by <code>filename</code> and incorporate or include
its entries into the table. Included files can include other files,
which can include other files, etc. For an example, see what files are
included by the entry include <samp><span class="file">en-us-g1.ctb</span></samp> in the table
<samp><span class="file">en-us-g2.ctb</span></samp>. If the included file is not in the same directory
as the main table, use a full path name for filename.
<p><a name="index-locale-94"></a><a name="locale-opcode"></a><br><dt><code>locale characters</code><dd>
Not implemented, but recognized and ignored for backward
compatibility.
<p><a name="index-undefined-95"></a><a name="undefined-opcode"></a><br><dt><code>undefined dots</code><dd>
If this opcode is used in a table any characters which have not been
defined in the table but are encountered in the text will be replaced by
the dot pattern. If this opcode is not used, any undefined characters
are replaced by <code>'\xhhhh'</code>, where the h's are hexadecimal digits.
<p><a name="index-display-96"></a><a name="display-opcode"></a><br><dt><code>display character dots</code><dd>
Associates dot patterns with the characters which will be sent to a
braille embosser, display or screen font. The character must be in the
range 0-255 and the dots must specify a single cell. Here are some
examples:
<pre class="example"> display a 1 When the character a is sent to the embosser or display,
it # will produce a dot 1.
</pre>
<pre class="example"> display L 123 When the character L is sent to the display or embosser
# produces dots 1-2-3.
</pre>
<p>The <code>display</code> opcode is optional. It is used when the embosser or
display has a different mapping of characters to dot patterns than
that given in <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a>. If used, display
entries must proceed character-definition entries.
<p><a name="index-multind-97"></a><a name="multind-opcode"></a><br><dt><code>multind dots opcode opcode ...</code><dd>
The <code>multind</code> opcode tells the back-translator that a sequence of
braille cells represents more than one braille indicator. For example,
in <samp><span class="file">en-us-g1.ctb</span></samp> we have <code>multind 56-6 letsign capsign</code>.
The back-translator can generally handle single braille indicators,
but it cannot apply them when they immediately follow each other. It
recognizes the letter sign if it is followed by a letter and takes
appropriate action. It also recognizes the capital sign if it is
followed by a letter. But when there is a letter sign followed by a
capital sign it fails to recognize the letter sign unless the sequence
has been defined with <code>multind</code>. A <code>multind</code> entry may not
contain a comment because liblouis would attempt to interpret it as an
opcode.
</dl>
<p><a name="Deprecated-Opcodes"></a>
<h3 class="section">3.13 Deprecated Opcodes</h3>
<p>The following opcodes are an early attempt to handle emphasis. They
have been deprecated by more specific opcodes, but are kept for
backward compatibility.
<a name="index-italsign-98"></a>
<dl><a name="italsign-opcode"></a><dt><code>italsign dots</code><dd>This opcode is deprecated. Use the <code>lastworditalbefore</code> opcode (see <a href="#lastworditalbefore-opcode">lastworditalbefore</a>) instead.
<p><a name="index-begital-99"></a><a name="begital-opcode"></a><br><dt><code>begital dots</code><dd>This opcode is deprecated. Use the <code>firstletterital</code> opcode (see <a href="#firstletterital-opcode">firstletterital</a>) instead.
<p><a name="index-endital-100"></a><a name="endital-opcode"></a><br><dt><code>endital dots</code><dd>This opcode is deprecated. Use the <code>lastletterital</code> opcode (see <a href="#lastletterital-opcode">lastletterital</a>) instead.
<p><a name="index-boldsign-101"></a><a name="boldsign-opcode"></a><br><dt><code>boldsign dots</code><dd>This opcode is deprecated. Use the <code>lastwordboldbefore</code> opcode (see <a href="#lastwordboldbefore-opcode">lastwordboldbefore</a>) instead.
<p><a name="index-begbold-102"></a><a name="begbold-opcode"></a><br><dt><code>begbold dots</code><dd>This opcode is deprecated. Use the <code>firstletterbold</code> opcode (see <a href="#firstletterbold-opcode">firstletterbold</a>) instead.
<p><a name="index-endbold-103"></a><a name="endbold-opcode"></a><br><dt><code>endbold dots</code><dd>This opcode is deprecated. Use the <code>lastletterbold</code> opcode (see <a href="#lastletterbold-opcode">lastletterbold</a>) instead.
<p><a name="index-undersign-104"></a><a name="undersign-opcode"></a><br><dt><code>undersign dots</code><dd>This opcode is deprecated. Use the <code>lastwordunderbefore</code> opcode (see <a href="#lastwordunderbefore-opcode">lastwordunderbefore</a>) instead.
<p><a name="index-begunder-105"></a><a name="begunder-opcode"></a><br><dt><code>begunder dots</code><dd>This opcode is deprecated. Use the <code>firstletterunder</code> opcode (see <a href="#firstletterunder-opcode">firstletterunder</a>) instead.
<p><a name="index-endunder-106"></a><a name="endunder-opcode"></a><br><dt><code>endunder dots</code><dd>This opcode is deprecated. Use the <code>lastletterunder</code> opcode (see <a href="#lastletterunder-opcode">lastletterunder</a>) instead.
<p><a name="index-literal-107"></a><a name="literal-opcode"></a><br><dt><code>literal characters</code><dd>This opcode is deprecated. Use the <code>compbrl</code> opcode (see <a href="#compbrl-opcode">compbrl</a>) instead.
</dl>
<p><a name="Notes-on-Back-Translation"></a>
<a name="Notes-on-Back_002dTranslation"></a>
<h2 class="chapter">4 Notes on Back-Translation</h2>
<p>Back-translation is carried out by the function
<code>lou_backTranslateString</code>. Its calling sequence is described in
<a href="#Programming-with-liblouis">Programming with liblouis</a>. Tables containing no
<code>context</code> opcode (see <a href="#context-opcode">context</a>), <code>correct</code> opcode (see <a href="#correct-opcode">correct</a>) or multipass opcodes can be
used for both forward and backward translation. If these opcodes are
needed different tables will be required.
<code>lou_backTranslateString</code> first performs <code>pass4</code>, if
present, then <code>pass3</code>, then <code>pass2</code>, then the
backtranslation, then corrections. Note that this is exactly the
inverse of forward translation.
<p><a name="Programming-with-liblouis"></a>
<h2 class="chapter">5 Programming with liblouis</h2>
<p><a name="License"></a>
<h3 class="section">5.1 License</h3>
<p>Liblouis may contain code borrowed from the Linux screen reader BRLTTY,
Copyright © 1999-2006 by the BRLTTY Team.
<p class="noindent">Copyright © 2004-2007 ViewPlus Technologies, Inc.
<a href="www.viewplus.com">www.viewplus.com</a>.
<p class="noindent">Copyright © 2007,2009 Abilitiessoft, Inc.
<a href="www.abilitiessoft.com">www.abilitiessoft.com</a>.
<p>Liblouis is free software: you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
<p>Liblouis is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
<p>You should have received a copy of the GNU Lesser General Public
License along with Liblouis. If not, see
<a href="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</a>.
<p><a name="Overview"></a>
<h3 class="section">5.2 Overview</h3>
<p>You use the liblouis library by calling the following functions,
<code>lou_translateString</code>, <code>lou_backTranslateString</code>,
<code>lou_logFile</code>, <code>lou_logPrint</code>,
<code>lou_endLog</code>, <code>lou_getTable</code>,
<code>lou_translate</code>, <code>lou_backTranslate</code>, <code>lou_hyphenate</code>,
<code>lou_charToDots</code>,
<code>lou_dotsToChar</code>,
<code>lou_compileString</code>, <code>lou_readCharFromFile</code>,
<code>lou_version</code> and <code>lou_free</code>.
These are described below. The header file, <samp><span class="file">liblouis.h</span></samp>, also
contains brief descriptions. Liblouis is written in straight C. It has
just three code modules, <samp><span class="file">compileTranslationTable.c</span></samp>,
<samp><span class="file">lou_translateString.c</span></samp> and <samp><span class="file">lou_backTranslateString.c</span></samp>. In
addition, there are two header files, <samp><span class="file">liblouis.h</span></samp>, which defines
the API, and <samp><span class="file">louis.h</span></samp>, used only internally and by liblouisxml.
The latter includes
<samp><span class="file">liblouis.h</span></samp>.
<p>Persons who wish to use liblouis from Python may want to skip ahead to
<a href="#Python-bindings">Python bindings</a>.
<p><samp><span class="file">compileTranslationTable.c</span></samp> keeps track of all translation tables
which an application has used. It is called by the translation,
hyphenation and checking functions when they start. If a table has not
yet been compiled <samp><span class="file">compileTranslationTable.c</span></samp> checks it for
correctness and compiles it into an efficient internal representation.
The main entry point is <code>lou_getTable</code>. Since it is the module
that keeps track of memory usage, it also contains the <code>lou_free</code>
function. In addition, it contains the <code>lou_logFile</code>,
<code>lou_logPrint</code> and <code>lou_endLog</code> functions, plus some utility
functions which are
used by the other modules.
<p>By default, liblouis handles all characters internally as 16-bit
unsigned integers. It can be compiled for 32-bit characters as
explained below. The meanings of these integers are not hard-coded.
Rather they are defined by the character-definition opcodes. However,
the standard printable characters, from decimal 32 to 126 are
recognized for the purpose of processing the opcodes. Hence, the
following definition is included in <samp><span class="file">liblouis.h</span></samp>. It is correct
for computers with at least 32-bit processors.
<pre class="example"> #define widechar unsigned short int
</pre>
<p>To make liblouis handle 32-bit Unicode simply remove the word
<code>short</code> in the above <code>define</code>. This will cause the translate and
back-translate functions to expect input in 32-bit form and to deliver
their output in this form. The input to the compiler (tables) is
unaffected except that two new escape sequences for 20-bit and 32-bit
characters are recognized.
<p>Here are the definitions of the eleven liblouis functions and their
parameters. They are given in terms of 16-bit Unicode. If liblouis has
been compiled for 32-bit Unicode simply read 32 instead of 16.
<p><a name="Data-structure-of-liblouis-tables"></a>
<h3 class="section">5.3 Data structure of liblouis tables</h3>
<p>The data structure <code>TranslationTableHeader</code> is defined by a
<code>typedef</code> statement in <samp><span class="file">louis.h</span></samp>. To find the beginning,
search for the word ‘<samp><span class="samp">header</span></samp>’. As its name implies, this is
actually the table header. Data are placed in the <code>ruleArea</code>
array, which is the last item defined in this structure. This array is
declared with a length of 1 and is expanded as needed. The table
header consists mostly of arrays of pointers of size <code>HASHNUM</code>.
These pointers are actually offsets into <code>ruleArea</code> and point to
chains of items which have been placed in the same hash bucket by a
simple hashing algorithm. <code>HASHNUM</code> should be a prime and is
currently 1123. The structure of the table was chosen to optimize
speed rather than memory usage.
<p>The first part of the table contains miscellaneous information, such
as the number of passes and whether various opcodes have been used. It
also contains the amount of memory allocated to the table and the
amount actually used.
<p>The next section contains pointers to various braille indicators and
begins with <code>capitalSign</code>. The rules pointed to contain the
dot pattern for the indicator and an opcode which is used by the
back-translator but does not appear in the list of opcodes. The
braille indicators also include various kinds of emphasis, such as
italic and bold and information about the length of emphasized
phrases. The latter is contained directly in the table item instead of
in a rule.
<p>After the braille indicators comes information about when a letter
sign should be used.
<p>Next is an array of size <code>HASHNUM</code> which points to character
definitions. These are created by the character-definition opcodes.
<p>Following this is a similar array pointing to definitions of
single-cell dot patterns. This is also created from the
character-definition opcodes. If a character definition contains a
multi-cell dot pattern this is compiled into ordinary forward and
backward rules. If such a multi-cell dot pattern contains a single
cell which has not previously been defined that cell is placed in this
array, but is given the attribute <code>space</code>.
<p>Next come arrays that map characters to single-cell dot patterns and
dots to characters. These are created from both character-definition
opcodes and display opcodes.
<p>Next is an array of size 256 which maps characters in this range to
dot patterns which may consist of multiple cells. It is used, for
example, to map ‘<samp><span class="samp">{</span></samp>’ to dots 456-246. These mappings are created
<!-- FIXME: the compdots opcode should be documented -->
<!-- by the @opcoderef{compdots} -->
by the <code>compdots</code>
or the <code>comp6</code> opcode (see <a href="#comp6-opcode">comp6</a>).
<p>Next are two small arrays that held pointers to chains of rules
produced by the <code>swapcd</code> opcode (see <a href="#swapcd-opcode">swapcd</a>) and the <code>swapdd</code> opcode (see <a href="#swapdd-opcode">swapdd</a>) and by
some multipass, <code>context</code> and <code>correct</code> opcodes.
<p>Now we get to an array of size <code>HASHNUM</code> which points to chains
of rules for forward translation.
<p>Following this is a similar array for back-translation.
<p>Finally is the <code>ruleArea</code>, an array of variable size to which
various structures are mapped and to which almost everything else
points.
<p><a name="lou_version"></a>
<a name="lou_005fversion"></a>
<h3 class="section">5.4 lou_version</h3>
<p><a name="index-lou_005fversion-108"></a>
<pre class="example"> char *lou_version ()
</pre>
<p>This function returns a pointer to a character string containing the
version of liblouis, plus other information, such as the release date
and perhaps notable changes.
<p><a name="lou_translateString"></a>
<a name="lou_005ftranslateString"></a>
<h3 class="section">5.5 lou_translateString</h3>
<p><a name="index-lou_005ftranslateString-109"></a>
<pre class="example"> int lou_translateString (
const char * tableList,
const widechar * inbuf,
int *inlen,
widechar *outbuf,
int *outlen,
char *typeform,
char *spacing,
int mode);
</pre>
<p>This function takes a string of 16-bit Unicode characters in
<code>inbuf</code> and translates it into a string of 16-bit characters in
<code>outbuf</code>. Each 16-bit character produces a particular dot pattern
in one braille cell when sent to an embosser or braille display or to
a screen type font. Which 16-bit character represents which dot pattern
is indicated by the character-definition and display opcodes in the
translation table.
<p><a name="translation_002dtables"></a>The <code>tableList</code> parameter points to a list of translation tables
separated by commas. If only one table is given, no comma should be
used after it. It is these tables which control just how the
translation is made, whether in Grade 2, Grade 1, or something else.
<p>liblouis knows where to find all the tables that have been distributed
with it. So you can just give a table name such as <code>en-us-g2.ctb</code>
and liblouis will load it. You can also give a table name which
includes a path. If this is the first table in a list, all the tables
in the list must be on the same path. You can specify a path on which
liblouis will look for table names by setting the environment variable
<code>LOUIS_TABLEPATH</code>. This environment variable can contain one or
more paths separated by commas. On receiving a table name liblouis
first checks to see if it can be found on any of these paths. If not,
it then checks to see if it can be found in the current directory, or,
if the first (or only) name in a table list, if it contains a
path name, can be found on that path. If not, it checks to see if it
can be found on the path where the distributed tables have been
installed. If a table has already been loaded and compiled this
path-checking is skipped.
<p>The tables in a list are all compiled into the same internal table.
The list is then regarded as the name of this table. As explained in
<a href="#How-to-Write-Translation-Tables">How to Write Translation Tables</a>, each table is a file which may
be plain text, big-endian Unicode or little-endian Unicode. A table
(or list of tables) is compiled into an internal representation the
first time it is used. Liblouis keeps track of which tables have been
compiled. For this reason, it is essential to call the <code>lou_free</code>
function at the end of your application to avoid memory leaks. Do
<em>NOT</em> call <code>lou_free</code> after each translation. This will
force liblouis to compile the translation tables each time they are
used, leading to great inefficiency.
<p>Note that both the <code>*inlen</code> and <code>*outlen</code> parameters are
pointers to integers. When the function is called, these integers
contain the maximum input and output lengths, respectively. When it
returns, they are set to the actual lengths used.
<p>The <code>typeform</code> parameter is used to indicate italic type,
boldface type, computer braille, etc. It is a string of characters
with the same length as the input buffer pointed to by <code>*inbuf</code>.
However, it is used to pass back character-by-character results, so
enough space must be provided to match the <code>*outlen</code> parameter.
Each character indicates the typeform of the corresponding character
in the input buffer. The values are as follows: 0 plain-text; 1
italic; 2 bold; 4 underline; 8 computer braille. These values can be
added for multiple emphasis. If this parameter is <code>NULL</code>, no
checking for type forms is done. In addition, if this parameter is not
<code>NULL</code>, it is set on return to have an 8 at every position
corresponding to a character in <code>outbuf</code> which was defined to
have a dot representation containing dot 7, dot 8 or both, and to 0
otherwise.
<p>The <code>spacing</code> parameter is used to indicate differences in
spacing between the input string and the translated output string. It
is also of the same length as the string pointed to by <code>*inbuf</code>.
If this parameter is <code>NULL</code>, no spacing information is computed.
<p>The <code>mode</code> parameter specifies how the translation should be
done. The valid values of mode are listed in <samp><span class="file">liblouis.h</span></samp>. They
are all powers of 2, so that a combined mode can be specified by
adding up different values.
<p>The function returns 1 if no errors were encountered and 0 if a
complete translation could not be done.
<p><a name="lou_translate"></a>
<a name="lou_005ftranslate"></a>
<h3 class="section">5.6 lou_translate</h3>
<p><a name="index-lou_005ftranslate-110"></a>
<pre class="example"> int lou_translate (
const char * tableList,
const widechar * const inbuf,
int *inlen,
widechar * outbuf,
int *outlen,
char *typeform,
char *spacing,
int *outputPos,
int *inputPos,
int *cursorPos,
int mode);
</pre>
<p>This function adds the parameters <code>outputPos</code>, <code>inputPos</code> and
<code>cursorPos</code>, to facilitate use in screen reader programs. The
<code>outputPos</code> parameter must point to an array of integers with at
least <code>inlen</code> elements. On return, this array will contain the
position in <code>outbuf</code> corresponding to each input position.
Similarly, <code>inputPos</code> must point to an array of integers of at
least <code>outlen</code> elements. On return, this array will contain the
position in <code>inbuf</code> corresponding to each position in <code>inbuf</code>.
<code>cursorPos</code> must point to an integer containing the position of the
cursor in the input. On return, it will contain the cursor position in
the output. Any parameter after <code>outlen</code> may be <code>NULL</code>. In
this case, the actions corresponding to it will not be carried out. The
<code>mode</code> parameter, however, must be present and must be an integer,
not a pointer to an integer. If the <code>compbrlAtCursor</code> bit is set in
the <code>mode</code> parameter the space-bounded characters containing the
cursor will be translated in computer braille. If the
<code>compbrlLeftCursor</code> bit is set only the characters to the left of
the cursor will be in computer braille. This bit overrides
<code>compbrlAtCursor</code>. The <code>ucBrl</code> (Unicode Braille) bit is used
by <code>lou_charToDots</code> and <code>lou_translate</code>. It causes the dot
patterns to be Unicode Braille rather than the liblouis representation.
<code>lou_dotsToChar</code> and <code>lou_backTranslate</code> recognize Unicode
braille automatically.
<p>The <code>otherTrans</code> mode needs special description. If it is set
liblouis will attempt to call a wrapper for another translator. These
other translators are usually for Asian languages. The calling sequence
is the same as for liblouis itself except that the <code>trantab</code>
parameter gives the name of the other translator, possibly abbreviated,
followed by a colon, followed by whatever other information the other
translator needs. This is specific for each translator. If no such
information is needed the colon should be omitted. The result of calling
either the translate or back-translate functions with this mode bit set
will be the same as calling without it set. That is, the wrapper for the
other translator simulates a call to liblouis. Note that the wrappers
are not implemented at this time. Setting this mode bit will result in
failure (return value of 0).
<p><a name="lou_backTranslateString"></a>
<a name="lou_005fbackTranslateString"></a>
<h3 class="section">5.7 lou_backTranslateString</h3>
<p><a name="index-lou_005fbackTranslateString-111"></a>
<pre class="example"> int lou_backTranslateString (
const char * tableList,
const widechar * inbuf,
int *inlen,
widechar *outbuf,
int *outlen,
char *typeform,
char *spacing,
int mode);
</pre>
<p>This is exactly the opposite of <code>lou_translateString</code>.
<code>inbuf</code> is a string of 16-bit Unicode characters representing
braille. <code>outbuf</code> will contain a string of 16–bit Unicode
characters. <code>typeform</code> will indicate any emphasis found in the
input string, while <code>spacing</code> will indicate any differences in
spacing between the input and output strings. The <code>typeform</code> and
<code>spacing</code> parameters may be <code>NULL</code> if this information is
not needed. <code>mode</code> again specifies how the back-translation
should be done.
<p><a name="lou_backTranslate"></a>
<a name="lou_005fbackTranslate"></a>
<h3 class="section">5.8 lou_backTranslate</h3>
<p><a name="index-lou_005fbackTranslate-112"></a>
<pre class="example"> int lou_backTranslate (
const char * tableList,
const widechar * inbufx,
int *inlen,
widechar * outbuf,
int *outlen,
char *typeform,
char *spacing,
int *outputPos,
int *inputPos,
int *cursorPos,
int mode);
</pre>
<p>This function is exactly the inverse of <code>lou_translate</code>.
<p><a name="lou_hyphenate"></a>
<a name="lou_005fhyphenate"></a>
<h3 class="section">5.9 lou_hyphenate</h3>
<p><a name="index-lou_005fhyphenate-113"></a>
<pre class="example"> int lou_hyphenate (
const char * tableList,
const widechar * const inbuf,
int inlen,
char *hyphens,
int mode);
</pre>
<p>This function looks at the characters in <code>inbuf</code> and if it finds
a sequence of letters attempts to hyphenate it as a word. Note
that lou_hyphenate operates on single words only, and spaces or
punctuation marks between letters are not allowed. Leading and
trailing punctuation marks are ignored. The table named by the
<code>tableList</code> parameter must contain a hyphenation table. If it does
not, the function does nothing. <code>inlen</code> is the length of the
character string in <code>inbuf</code>. <code>hyphens</code> is an array of
characters and must be of size <code>inlen</code>. If hyphenation is
successful it will have a 1 at the beginning of each syllable and a 0
elsewhere. If the <code>mode</code> parameter is 0 <code>inbuf</code> is assumed
to contain untranslated characters. Any nonzero value means that
<code>inbuf</code> contains a translation. In this case, it is
back-translated, hyphenation is performed, and it is re-translated so
that the hyphens can be placed correctly. The <code>lou_translate</code> and
<code>lou_backTranslate</code> functions are used in this process.
<code>lou_hyphenate</code> returns 1 if hyphenation was successful and 0
otherwise. In the latter case, the contents of the <code>hyphens</code>
parameter are undefined. This function was provided for use in
liblouisxml.
<p><a name="lou_compileString"></a>
<a name="lou_005fcompileString"></a>
<h3 class="section">5.10 lou_compileString</h3>
<p><a name="index-lou_005fcompileString-114"></a>
<pre class="example"> int lou_compileString (const char *tableList, const char *inString)
</pre>
<p>This function enables you to compile a table entry on the fly at
run-time. The new entry is added to <code>tableList</code> and remains in force
until <code>lou_free</code> is called. If <code>tableList</code> has not previously
been loaded it is loaded and compiled. <code>inString</code> contains the
table entry to be added. It may be anything valid. Error messages
will be produced if it is invalid. The function returns 1 on success and
0 on failure.
<p><a name="lou_dotsToChar"></a>
<a name="lou_005fdotsToChar"></a>
<h3 class="section">5.11 lou_dotsToChar</h3>
<p><a name="index-lou_005fdotsToChar-115"></a>
<pre class="example"> int lou_dotsToChar (const char *tableList, const widechar *inbuf, widechar
*outbuf, int length, int)
</pre>
<p>This function takes a widechar string in <code>inbuf</code> consisting of dot
patterns and converts it to a widechar string in <code>outbuf</code>
consisting of characters according to the specifications in
<code>tableList</code>. <code>length</code> is the length of both <code>inbuf</code> and
<code>outbuf</code>. The dot patterns in <code>inbuf</code> can be in either
liblouis format or Unicode braille. The function returns 1 on success
and 0 on failure.
<p><a name="lou_charToDots"></a>
<a name="lou_005fcharToDots"></a>
<h3 class="section">5.12 lou_charToDots</h3>
<p><a name="index-lou_005fcharToDots-116"></a>
<pre class="example"> int lou_charToDots (const char *tableList, const widechar *inbuf, widechar
*outbuf, int length, int mode)
</pre>
<p>This function is the inverse of <code>lou_dotsToChar</code>. It takes a
widechar string in <code>inbuf</code> consisting of characters and converts it
to a widechar string in <code>outbuf</code> consisting of dot patterns
according to the specifications in <code>tableList</code>. <code>length</code> is the
length of both <code>inbuf</code> and <code>outbuf</code>. The dot patterns in
<code>outbufbuf</code> are in liblouis format if the mode bit <code>ucBrl</code> is
not set and in Unicode format if it is set. The function returns 1 on
success and 0 on failure.
<p><a name="lou_logFile"></a>
<a name="lou_005flogFile"></a>
<h3 class="section">5.13 lou_logFile</h3>
<p><a name="index-lou_005flogFile-117"></a>
<pre class="example"> void lou_logFile (char *fileName);
</pre>
<p>This function is used when it is not convenient either to let messages
be printed on stderr or to use redirection, as when liblouis is used
in a GUI application or in liblouisxml. Any error messages generated
will be printed to the file given in this call. The entire path name of
the file must be given.
<p><a name="lou_logPrint"></a>
<a name="lou_005flogPrint"></a>
<h3 class="section">5.14 lou_logPrint</h3>
<p><a name="index-lou_005flogPrint-118"></a>
<pre class="example"> void lou_logPrint (char *format, ...);
</pre>
<p>This function is called like <code>fprint</code>. It can be used by other
libraries to print messages to the file specified by the call to
<code>lou_logFile</code>. In particular, it is used by the companion
library liblouisxml.
<p><a name="lou_logEnd"></a>
<a name="lou_005flogEnd"></a>
<h3 class="section">5.15 lou_logEnd</h3>
<p><a name="index-lou_005flogEnd-119"></a>
<pre class="example"> lou_logEnd ();
</pre>
<p>This function is used at the end of processing a document to close the
log file, so that it can be read by the rest of the program.
<p><a name="lou_setDataPath"></a>
<a name="lou_005fsetDataPath"></a>
<h3 class="section">5.16 lou_setDataPath</h3>
<p><a name="index-lou_005fsetDataPath-120"></a>
<pre class="example"> char * lou_setDataPath (char *path);
</pre>
<p>This function is used to tell liblouis and liblouisutdml where tables
and files are located. It thus makes them completely relocatable, even
on Linux. The <code>path</code> is the directory where the subdirectories
<code>liblouis/tables</code> and <code>liblouisutdml/lbu_files</code> are rooted or
located. The function returns a pointer to the <code>path</code>.
<p><a name="lou_getDataPath"></a>
<a name="lou_005fgetDataPath"></a>
<h3 class="section">5.17 lou_getDataPath</h3>
<p><a name="index-lou_005fgetDataPath-121"></a>
<pre class="example"> char * lou_getDataPath ();
</pre>
<p>This function returns a pointer to the path set by
<code>lou_setDataPath</code>. If no path has been set it returns <code>NULL</code>.
<p><a name="lou_getTable"></a>
<a name="lou_005fgetTable"></a>
<h3 class="section">5.18 lou_getTable</h3>
<p><a name="index-lou_005fgetTable-122"></a>
<pre class="example"> void *lou_getTable (char *tablelist);
</pre>
<p><code>tablelist</code> is a list of names of table files separated by
commas, as explained previously
(see <a href="#translation_002dtables"><code>tableList</code> parameter in <code>lou_translateString</code></a>). If no errors are found this function
returns a pointer to the compiled table. If errors are found messages
are printed to the log file, which is stderr unless a different
filename has been given using the <code>lou_logFile</code> function.
Errors result in a <code>NULL</code> pointer being returned.
<p><a name="lou_readCharFromFile"></a>
<a name="lou_005freadCharFromFile"></a>
<h3 class="section">5.19 lou_readCharFromFile</h3>
<p><a name="index-lou_005freadCharFromFile-123"></a>
<pre class="example"> int lou_readCharFromFile (const char *fileName, int *mode);
</pre>
<p>This function is provided for situations where it is necessary to read
a file which may contain little-endian or big-endian 16-bit Unicode
characters or ASCII8 characters. The return value is a little-endian
character, encoded as an integer. The <code>fileName</code> parameter is the
name of the file to be read. The <code>mode</code> parameter is a pointer to
an integer which must be set to 1 on the first call. After that, the
function takes care of it. On end-of-file the function returns
<code>EOF</code>.
<p><a name="lou_free"></a>
<a name="lou_005ffree"></a>
<h3 class="section">5.20 lou_free</h3>
<p><a name="index-lou_005ffree-124"></a>
<pre class="example"> void lou_free ();
</pre>
<p>This function should be called at the end of the application to free
all memory allocated by liblouis. Failure to do so will result in
memory leaks. Do <em>NOT</em> call <code>lou_free</code> after each
translation. This will force liblouis to compile the translation
tables every time they are used, resulting in great inefficiency.
<p><a name="Python-bindings"></a>
<h3 class="section">5.21 Python bindings</h3>
<p>There are Python bindings for <code>lou_translateString</code>,
<code>lou_translate</code> and <code>lou_version</code>. For installation
instructions see the the <samp><span class="file">README</span></samp> file in the <samp><span class="file">python</span></samp>
directory. Usage information is included in the Python module itself.
<p><a name="Opcode-Index"></a>
<h2 class="unnumbered">Opcode Index</h2>
<ul class="index-opcode" compact>
<li><a href="#index-after-83">after</a>: <a href="#Character_002dClass-Opcodes">Character-Class Opcodes</a></li>
<li><a href="#index-always-57">always</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-before-84">before</a>: <a href="#Character_002dClass-Opcodes">Character-Class Opcodes</a></li>
<li><a href="#index-begbold-102">begbold</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-begcaps-18">begcaps</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-begcomp-46">begcomp</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-begital-99">begital</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-begmidword-70">begmidword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-begnum-78">begnum</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-begunder-105">begunder</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-begword-69">begword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-boldsign-101">boldsign</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-capsign-17">capsign</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-capsnocont-50">capsnocont</a>: <a href="#Special-Processing-Opcodes">Special Processing Opcodes</a></li>
<li><a href="#index-class-82">class</a>: <a href="#Character_002dClass-Opcodes">Character-Class Opcodes</a></li>
<li><a href="#index-comp6-54">comp6</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-compbrl-53">compbrl</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-context-88">context</a>: <a href="#The-Context-and-Multipass-Opcodes">The Context and Multipass Opcodes</a></li>
<li><a href="#index-contraction-66">contraction</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-correct-92">correct</a>: <a href="#The-correct-Opcode">The correct Opcode</a></li>
<li><a href="#index-decpoint-48">decpoint</a>: <a href="#Special-Symbol-Opcodes">Special Symbol Opcodes</a></li>
<li><a href="#index-digit-8">digit</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-display-96">display</a>: <a href="#Miscellaneous-Opcodes">Miscellaneous Opcodes</a></li>
<li><a href="#index-endbold-103">endbold</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-endcaps-19">endcaps</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-endcomp-47">endcomp</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-endital-100">endital</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-endnum-80">endnum</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-endunder-106">endunder</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-endword-73">endword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-exactdots-75">exactdots</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-firstletterbold-35">firstletterbold</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-firstletterital-28">firstletterital</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-firstletterunder-42">firstletterunder</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-firstwordbold-32">firstwordbold</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-firstwordital-25">firstwordital</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-firstwordunder-39">firstwordunder</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-grouping-10">grouping</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-hyphen-49">hyphen</a>: <a href="#Special-Symbol-Opcodes">Special Symbol Opcodes</a></li>
<li><a href="#index-include-93">include</a>: <a href="#Miscellaneous-Opcodes">Miscellaneous Opcodes</a></li>
<li><a href="#index-italsign-98">italsign</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-joinnum-81">joinnum</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-joinword-64">joinword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-largesign-60">largesign</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-lastletterbold-36">lastletterbold</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastletterital-29">lastletterital</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastletterunder-43">lastletterunder</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastwordboldafter-34">lastwordboldafter</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastwordboldbefore-33">lastwordboldbefore</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastworditalafter-27">lastworditalafter</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastworditalbefore-26">lastworditalbefore</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastwordunderafter-41">lastwordunderafter</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lastwordunderbefore-40">lastwordunderbefore</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lenboldphrase-38">lenboldphrase</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lenitalphrase-31">lenitalphrase</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-lenunderphrase-45">lenunderphrase</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-letsign-20">letsign</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-letter-11">letter</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-litdigit-14">litdigit</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-literal-107">literal</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-locale-94">locale</a>: <a href="#Miscellaneous-Opcodes">Miscellaneous Opcodes</a></li>
<li><a href="#index-lowercase-12">lowercase</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-lowword-65">lowword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-math-16">math</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-midendword-72">midendword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-midnum-79">midnum</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-midword-71">midword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-multind-97">multind</a>: <a href="#Miscellaneous-Opcodes">Miscellaneous Opcodes</a></li>
<li><a href="#index-noback-51">noback</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-nocont-55">nocont</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-nocross-63">nocross</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-nofor-52">nofor</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-noletsign-21">noletsign</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-noletsignafter-23">noletsignafter</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-noletsignbefore-22">noletsignbefore</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-numsign-24">numsign</a>: <a href="#Braille-Indicator-Opcodes">Braille Indicator Opcodes</a></li>
<li><a href="#index-partword-74">partword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-pass2-89">pass2</a>: <a href="#The-Context-and-Multipass-Opcodes">The Context and Multipass Opcodes</a></li>
<li><a href="#index-pass3-90">pass3</a>: <a href="#The-Context-and-Multipass-Opcodes">The Context and Multipass Opcodes</a></li>
<li><a href="#index-pass4-91">pass4</a>: <a href="#The-Context-and-Multipass-Opcodes">The Context and Multipass Opcodes</a></li>
<li><a href="#index-postpunc-77">postpunc</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-prepunc-76">prepunc</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-prfword-68">prfword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-punctuation-7">punctuation</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-repeated-58">repeated</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-replace-56">replace</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-repword-59">repword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-sign-15">sign</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-singleletterbold-37">singleletterbold</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-singleletterital-30">singleletterital</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-singleletterunder-44">singleletterunder</a>: <a href="#Emphasis-Opcodes">Emphasis Opcodes</a></li>
<li><a href="#index-space-6">space</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-sufword-67">sufword</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-swapcc-87">swapcc</a>: <a href="#Swap-Opcodes">Swap Opcodes</a></li>
<li><a href="#index-swapcd-85">swapcd</a>: <a href="#Swap-Opcodes">Swap Opcodes</a></li>
<li><a href="#index-swapdd-86">swapdd</a>: <a href="#Swap-Opcodes">Swap Opcodes</a></li>
<li><a href="#index-syllable-62">syllable</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
<li><a href="#index-undefined-95">undefined</a>: <a href="#Miscellaneous-Opcodes">Miscellaneous Opcodes</a></li>
<li><a href="#index-undersign-104">undersign</a>: <a href="#Deprecated-Opcodes">Deprecated Opcodes</a></li>
<li><a href="#index-uplow-9">uplow</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-uppercase-13">uppercase</a>: <a href="#Character_002dDefinition-Opcodes">Character-Definition Opcodes</a></li>
<li><a href="#index-word-61">word</a>: <a href="#Translation-Opcodes">Translation Opcodes</a></li>
</ul><p><a name="Function-Index"></a>
<h2 class="unnumbered">Function Index</h2>
<ul class="index-fn" compact>
<li><a href="#index-lou_005fbackTranslate-112"><code>lou_backTranslate</code></a>: <a href="#lou_005fbackTranslate">lou_backTranslate</a></li>
<li><a href="#index-lou_005fbackTranslateString-111"><code>lou_backTranslateString</code></a>: <a href="#lou_005fbackTranslateString">lou_backTranslateString</a></li>
<li><a href="#index-lou_005fcharToDots-116"><code>lou_charToDots</code></a>: <a href="#lou_005fcharToDots">lou_charToDots</a></li>
<li><a href="#index-lou_005fcompileString-114"><code>lou_compileString</code></a>: <a href="#lou_005fcompileString">lou_compileString</a></li>
<li><a href="#index-lou_005fdotsToChar-115"><code>lou_dotsToChar</code></a>: <a href="#lou_005fdotsToChar">lou_dotsToChar</a></li>
<li><a href="#index-lou_005ffree-124"><code>lou_free</code></a>: <a href="#lou_005ffree">lou_free</a></li>
<li><a href="#index-lou_005fgetDataPath-121"><code>lou_getDataPath</code></a>: <a href="#lou_005fgetDataPath">lou_getDataPath</a></li>
<li><a href="#index-lou_005fgetTable-122"><code>lou_getTable</code></a>: <a href="#lou_005fgetTable">lou_getTable</a></li>
<li><a href="#index-lou_005fhyphenate-113"><code>lou_hyphenate</code></a>: <a href="#lou_005fhyphenate">lou_hyphenate</a></li>
<li><a href="#index-lou_005flogEnd-119"><code>lou_logEnd</code></a>: <a href="#lou_005flogEnd">lou_logEnd</a></li>
<li><a href="#index-lou_005flogFile-117"><code>lou_logFile</code></a>: <a href="#lou_005flogFile">lou_logFile</a></li>
<li><a href="#index-lou_005flogPrint-118"><code>lou_logPrint</code></a>: <a href="#lou_005flogPrint">lou_logPrint</a></li>
<li><a href="#index-lou_005freadCharFromFile-123"><code>lou_readCharFromFile</code></a>: <a href="#lou_005freadCharFromFile">lou_readCharFromFile</a></li>
<li><a href="#index-lou_005fsetDataPath-120"><code>lou_setDataPath</code></a>: <a href="#lou_005fsetDataPath">lou_setDataPath</a></li>
<li><a href="#index-lou_005ftranslate-110"><code>lou_translate</code></a>: <a href="#lou_005ftranslate">lou_translate</a></li>
<li><a href="#index-lou_005ftranslateString-109"><code>lou_translateString</code></a>: <a href="#lou_005ftranslateString">lou_translateString</a></li>
<li><a href="#index-lou_005fversion-108"><code>lou_version</code></a>: <a href="#lou_005fversion">lou_version</a></li>
</ul><p><a name="Program-Index"></a>
<h2 class="unnumbered">Program Index</h2>
<ul class="index-pg" compact>
<li><a href="#index-lou_005fallround-3"><code>lou_allround</code></a>: <a href="#lou_005fallround">lou_allround</a></li>
<li><a href="#index-lou_005fcheckhyphens-5"><code>lou_checkhyphens</code></a>: <a href="#lou_005fcheckhyphens">lou_checkhyphens</a></li>
<li><a href="#index-lou_005fchecktable-2"><code>lou_checktable</code></a>: <a href="#lou_005fchecktable">lou_checktable</a></li>
<li><a href="#index-lou_005fdebug-1"><code>lou_debug</code></a>: <a href="#lou_005fdebug">lou_debug</a></li>
<li><a href="#index-lou_005ftranslate-4"><code>lou_translate</code></a>: <a href="#lou_005ftranslate-_0028program_0029">lou_translate (program)</a></li>
</ul></body></html>
