<html lang="en">
<head>
<title>Parser - GNU Octave</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="GNU Octave">
<meta name="generator" content="makeinfo 4.13">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Grammar-and-Parser.html#Grammar-and-Parser" title="Grammar and Parser">
<link rel="prev" href="Keywords.html#Keywords" title="Keywords">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
pre.display { font-family:inherit }
pre.format { font-family:inherit }
pre.smalldisplay { font-family:inherit; font-size:smaller }
pre.smallformat { font-family:inherit; font-size:smaller }
pre.smallexample { font-size:smaller }
pre.smalllisp { font-size:smaller }
span.sc { font-variant:small-caps }
span.roman { font-family:serif; font-weight:normal; }
span.sansserif { font-family:sans-serif; font-weight:normal; }
--></style>
</head>
<body>
<div class="node">
<a name="Parser"></a>
<p>
Previous: <a rel="previous" accesskey="p" href="Keywords.html#Keywords">Keywords</a>,
Up: <a rel="up" accesskey="u" href="Grammar-and-Parser.html#Grammar-and-Parser">Grammar and Parser</a>
<hr>
</div>
<h3 class="section">I.2 Parser</h3>
<p><a name="index-parser-3464"></a>
The parser has a number of variables that affect its internal operation.
These variables are generally documented in the manual alongside the code that
they affect. For example, <code>allow_noninteger_range_as_index</code> is discussed
in the section on index expressions.
<p>In addition, there are three non-specific parser customization functions.
<code>add_input_event_hook</code> can be used to schedule a user function for
periodic evaluation. <code>remove_input_event_hook</code> will stop a user function
from being evaluated periodically.
<!-- add_input_event_hook src/input.cc -->
<p><a name="doc_002dadd_005finput_005fevent_005fhook"></a>
<div class="defun">
— Built-in Function: <b>add_input_event_hook</b> (<var>fcn</var>)<var><a name="index-add_005finput_005fevent_005fhook-3465"></a></var><br>
— Built-in Function: <b>add_input_event_hook</b> (<var>fcn, data</var>)<var><a name="index-add_005finput_005fevent_005fhook-3466"></a></var><br>
<blockquote><p>Add the named function <var>fcn</var> to the list of functions to call
periodically when Octave is waiting for input. The function should
have the form
<pre class="example"> <var>fcn</var> (<var>data</var>)
</pre>
<p>If <var>data</var> is omitted, Octave calls the function without any
arguments.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dremove_005finput_005fevent_005fhook.html#doc_002dremove_005finput_005fevent_005fhook">remove_input_event_hook</a>.
</p></blockquote></div>
<!-- remove_input_event_hook src/input.cc -->
<p><a name="doc_002dremove_005finput_005fevent_005fhook"></a>
<div class="defun">
— Built-in Function: <b>remove_input_event_hook</b> (<var>fcn</var>)<var><a name="index-remove_005finput_005fevent_005fhook-3467"></a></var><br>
<blockquote><p>Remove the named function <var>fcn</var> from the list of functions to call
periodically when Octave is waiting for input.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dadd_005finput_005fevent_005fhook.html#doc_002dadd_005finput_005fevent_005fhook">add_input_event_hook</a>.
</p></blockquote></div>
<p>Finally, when the parser cannot identify an input token it calls a particular
function to handle this. By default, this is the function "unimplemented"
which makes suggestions about possible Octave substitutes for <span class="sc">matlab</span>
functions.
<!-- missing_function_hook src/variables.cc -->
<p><a name="doc_002dmissing_005ffunction_005fhook"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>missing_function_hook</b> ()<var><a name="index-missing_005ffunction_005fhook-3468"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>missing_function_hook</b> (<var>new_val</var>)<var><a name="index-missing_005ffunction_005fhook-3469"></a></var><br>
— Built-in Function: <b>missing_function_hook</b> (<var>new_val, "local"</var>)<var><a name="index-missing_005ffunction_005fhook-3470"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies the function to call when
an unknown identifier is requested.
<p>When called from inside a function with the "local" option, the variable is
changed locally for the function and any subroutines it calls. The original
variable value is restored when exiting the function.
</p></blockquote></div>
<!-- DO NOT EDIT! Generated automatically by munge-texi.pl. -->
</body></html>
