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<title>Scanf</title>
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<center><h1>Module <a href="type_Scanf.html">Scanf</a></h1></center>
<br>
<pre><span class="keyword">module</span> Scanf: <code class="code"><span class="keyword">sig</span></code> <a href="Scanf.html">..</a> <code class="code"><span class="keyword">end</span></code></pre>Formatted input functions.<br>
<hr width="100%">
<br>
<a name="6_Introduction"></a>
<h6>Introduction</h6><br>
<br>
<a name="7_Functionalinputwithformatstrings"></a>
<div class="h7">Functional input with format strings</div><br>
<br>
The module <code class="code"><span class="constructor">Scanf</span></code> provides formatted input functions or <em>scanners</em>.
<p>
The formatted input functions can read from any kind of input, including
strings, files, or anything that can return characters. The more general
source of characters is named a <em>scanning buffer</em> and has type
<a href="Scanf.Scanning.html#TYPEscanbuf"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.scanbuf</code></a>. The more general formatted input function reads from
any scanning buffer and is named <code class="code">bscanf</code>.
<p>
Generally speaking, the formatted input functions have 3 arguments:<ul>
<li>the first argument is a source of characters for the input,</li>
<li>the second argument is a format string that specifies the values to
read,</li>
<li>the third argument is a <em>receiver function</em> that is applied to the
values read.</li>
</ul>
Hence, a typical call to the formatted input function <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a> is
<code class="code">bscanf ib fmt f</code>, where:
<p>
<ul>
<li><code class="code">ib</code> is a source of characters (typically a <em> scanning buffer</em> with type <a href="Scanf.Scanning.html#TYPEscanbuf"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.scanbuf</code></a>),</li>
</ul>
<ul>
<li><code class="code">fmt</code> is a format string (the same format strings as those used to print
material with module <a href="Printf.html"><code class="code"><span class="constructor">Printf</span></code></a> or <a href="Format.html"><code class="code"><span class="constructor">Format</span></code></a>),</li>
</ul>
<ul>
<li><code class="code">f</code> is a function that has as many arguments as the number of values to
read in the input.</li>
</ul>
<br>
<br>
<a name="7_Asimpleexample"></a>
<div class="h7">A simple example</div><br>
<br>
As suggested above, the expression <code class="code">bscanf ib <span class="string">"%d"</span> f</code> reads a decimal
integer <code class="code">n</code> from the source of characters <code class="code">ib</code> and returns <code class="code">f n</code>.
<p>
For instance,
<p>
<ul>
<li>if we use <code class="code">stdib</code> as the source of characters (<a href="Scanf.Scanning.html#VALstdib"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.stdib</code></a> is
the predefined input buffer that reads from standard input),</li>
</ul>
<ul>
<li>if we define the receiver <code class="code">f</code> as <code class="code"><span class="keyword">let</span> f x = x + 1</code>,</li>
</ul>
then <code class="code">bscanf stdib <span class="string">"%d"</span> f</code> reads an integer <code class="code">n</code> from the standard input
and returns <code class="code">f n</code> (that is <code class="code">n + 1</code>). Thus, if we evaluate <code class="code">bscanf stdib
<span class="string">"%d"</span> f</code>, and then enter <code class="code">41</code> at the keyboard, we get <code class="code">42</code> as the final
result.<br>
<br>
<a name="7_Formattedinputasafunctionalfeature"></a>
<div class="h7">Formatted input as a functional feature</div><br>
<br>
The Caml scanning facility is reminiscent of the corresponding C feature.
However, it is also largely different, simpler, and yet more powerful:
the formatted input functions are higher-order functionals and the
parameter passing mechanism is just the regular function application not
the variable assigment based mechanism which is typical for formatted
input in imperative languages; the Caml format strings also feature
useful additions to easily define complex tokens; as expected within a
functional programming language, the formatted input functions also
support polymorphism, in particular arbitrary interaction with
polymorphic user-defined scanners. Furthermore, the Caml formatted input
facility is fully type-checked at compile time.<br>
<pre><span class="keyword">module</span> <a href="Scanf.Scanning.html">Scanning</a>: <code class="code"><span class="keyword">sig</span></code> <a href="Scanf.Scanning.html">..</a> <code class="code"><span class="keyword">end</span></code></pre><div class="info">
Scanning buffers
</div>
<br>
<a name="6_Typeofformattedinputfunctions"></a>
<h6>Type of formatted input functions</h6><br>
<pre><span class="keyword">type</span> <a name="TYPEscanner"></a><code class="type">('a, 'b, 'c, 'd)</code> scanner = <code class="type">('a, <a href="Scanf.Scanning.html#TYPEscanbuf">Scanning.scanbuf</a>, 'b, 'c, 'a -> 'd, 'd) format6 -> 'c</code> </pre>
<div class="info">
The type of formatted input scanners: <code class="code">(<span class="keywordsign">'</span>a, <span class="keywordsign">'</span>b, <span class="keywordsign">'</span>c, <span class="keywordsign">'</span>d) scanner</code> is the
type of a formatted input function that reads from some scanning buffer
according to some format string; more precisely, if <code class="code">scan</code> is some
formatted input function, then <code class="code">scan ib fmt f</code> applies <code class="code">f</code> to the arguments
specified by the format string <code class="code">fmt</code>, when <code class="code">scan</code> has read those arguments
from the scanning input buffer <code class="code">ib</code>.
<p>
For instance, the <code class="code">scanf</code> function below has type <code class="code">(<span class="keywordsign">'</span>a, <span class="keywordsign">'</span>b, <span class="keywordsign">'</span>c, <span class="keywordsign">'</span>d)
scanner</code>, since it is a formatted input function that reads from <code class="code">stdib</code>:
<code class="code">scanf fmt f</code> applies <code class="code">f</code> to the arguments specified by <code class="code">fmt</code>, reading
those arguments from <code class="code">stdin</code> as expected.
<p>
If the format <code class="code">fmt</code> has some <code class="code">%r</code> indications, the corresponding input
functions must be provided before the receiver <code class="code">f</code> argument. For
instance, if <code class="code">read_elem</code> is an input function for values of type <code class="code">t</code>,
then <code class="code">bscanf ib <span class="string">"%r;"</span> read_elem f</code> reads a value <code class="code">v</code> of type <code class="code">t</code> followed
by a <code class="code"><span class="string">';'</span></code> character, and returns <code class="code">f v</code>.<br>
</div>
<pre><span class="keyword">exception</span> <a name="EXCEPTIONScan_failure"></a>Scan_failure <span class="keyword">of</span> <code class="type">string</code></pre>
<div class="info">
The exception that formatted input functions raise when the input cannot be
read according to the given format.<br>
</div>
<br>
<a name="6_Thegeneralformattedinputfunction"></a>
<h6>The general formatted input function</h6><br>
<pre><span class="keyword">val</span> <a name="VALbscanf"></a>bscanf : <code class="type"><a href="Scanf.Scanning.html#TYPEscanbuf">Scanning.scanbuf</a> -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info">
<code class="code">bscanf ib fmt r1 ... rN f</code> reads arguments for the function <code class="code">f</code>, from the
scanning buffer <code class="code">ib</code>, according to the format string <code class="code">fmt</code>, and applies <code class="code">f</code>
to these values.
The result of this call to <code class="code">f</code> is returned as the result of the entire
<code class="code">bscanf</code> call.
For instance, if <code class="code">f</code> is the function <code class="code"><span class="keyword">fun</span> s i <span class="keywordsign">-></span> i + 1</code>, then
<code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"x= 1"</span> <span class="string">"%s = %i"</span> f</code> returns <code class="code">2</code>.
<p>
Arguments <code class="code">r1</code> to <code class="code">rN</code> are user-defined input functions that read the
argument corresponding to a <code class="code">%r</code> conversion.<br>
</div>
<br>
<a name="6_Formatstringdescription"></a>
<h6>Format string description</h6><br>
<br>
The format is a character string which contains three types of
objects:<ul>
<li>plain characters, which are simply matched with the characters of the
input,</li>
<li>conversion specifications, each of which causes reading and conversion of
one argument for the function <code class="code">f</code>,</li>
<li>scanning indications to specify boundaries of tokens.</li>
</ul>
<br>
<br>
<a name="7_Thespacecharacterinformatstrings"></a>
<div class="h7">The space character in format strings</div><br>
<br>
As mentioned above, a plain character in the format string is just
matched with the characters of the input; however, one character is a
special exception to this simple rule: the space character (ASCII code
32) does not match a single space character, but any amount of
``whitespace'' in the input. More precisely, a space inside the format
string matches <em>any number</em> of tab, space, line feed and carriage
return characters.
<p>
Matching <em>any</em> amount of whitespace, a space in the format string
also matches no amount of whitespace at all; hence, the call <code class="code">bscanf ib
<span class="string">"Price = %d $"</span> (<span class="keyword">fun</span> p <span class="keywordsign">-></span> p)</code> succeds and returns <code class="code">1</code> when reading an
input with various whitespace in it, such as <code class="code"><span class="constructor">Price</span> = 1 $</code>,
<code class="code"><span class="constructor">Price</span> = 1 $</code>, or even <code class="code"><span class="constructor">Price</span>=1$</code>.<br>
<br>
<a name="7_Conversionspecificationsinformatstrings"></a>
<div class="h7">Conversion specifications in format strings</div><br>
<br>
Conversion specifications consist in the <code class="code">%</code> character, followed by
an optional flag, an optional field width, and followed by one or
two conversion characters. The conversion characters and their
meanings are:
<p>
<ul>
<li><code class="code">d</code>: reads an optionally signed decimal integer.</li>
<li><code class="code">i</code>: reads an optionally signed integer
(usual input formats for hexadecimal (<code class="code">0x[d]+</code> and <code class="code">0<span class="constructor">X</span>[d]+</code>),
octal (<code class="code">0o[d]+</code>), and binary <code class="code">0b[d]+</code> notations are understood).</li>
<li><code class="code">u</code>: reads an unsigned decimal integer.</li>
<li><code class="code">x</code> or <code class="code"><span class="constructor">X</span></code>: reads an unsigned hexadecimal integer.</li>
<li><code class="code">o</code>: reads an unsigned octal integer.</li>
<li><code class="code">s</code>: reads a string argument that spreads as much as possible, until the
following bounding condition holds: a whitespace has been found, a
scanning indication has been encountered, or the end-of-input has been
reached.
Hence, this conversion always succeeds: it returns an empty
string, if the bounding condition holds when the scan begins.</li>
<li><code class="code"><span class="constructor">S</span></code>: reads a delimited string argument (delimiters and special
escaped characters follow the lexical conventions of Caml).</li>
<li><code class="code">c</code>: reads a single character. To test the current input character
without reading it, specify a null field width, i.e. use
specification <code class="code">%0c</code>. Raise <code class="code"><span class="constructor">Invalid_argument</span></code>, if the field width
specification is greater than 1.</li>
<li><code class="code"><span class="constructor">C</span></code>: reads a single delimited character (delimiters and special
escaped characters follow the lexical conventions of Caml).</li>
<li><code class="code">f</code>, <code class="code">e</code>, <code class="code"><span class="constructor">E</span></code>, <code class="code">g</code>, <code class="code"><span class="constructor">G</span></code>: reads an optionally signed
floating-point number in decimal notation, in the style <code class="code">dddd.ddd
e/<span class="constructor">E</span>+-dd</code>.</li>
<li><code class="code"><span class="constructor">F</span></code>: reads a floating point number according to the lexical
conventions of Caml (hence the decimal point is mandatory if the
exponent part is not mentioned).</li>
<li><code class="code"><span class="constructor">B</span></code>: reads a boolean argument (<code class="code"><span class="keyword">true</span></code> or <code class="code"><span class="keyword">false</span></code>).</li>
<li><code class="code">b</code>: reads a boolean argument (for backward compatibility; do not use
in new programs).</li>
<li><code class="code">ld</code>, <code class="code">li</code>, <code class="code">lu</code>, <code class="code">lx</code>, <code class="code">lX</code>, <code class="code">lo</code>: reads an <code class="code">int32</code> argument to
the format specified by the second letter (decimal, hexadecimal, etc).</li>
<li><code class="code">nd</code>, <code class="code">ni</code>, <code class="code">nu</code>, <code class="code">nx</code>, <code class="code">nX</code>, <code class="code">no</code>: reads a <code class="code">nativeint</code> argument to
the format specified by the second letter.</li>
<li><code class="code"><span class="constructor">Ld</span></code>, <code class="code"><span class="constructor">Li</span></code>, <code class="code"><span class="constructor">Lu</span></code>, <code class="code"><span class="constructor">Lx</span></code>, <code class="code"><span class="constructor">LX</span></code>, <code class="code"><span class="constructor">Lo</span></code>: reads an <code class="code">int64</code> argument to
the format specified by the second letter.</li>
<li><code class="code">[ range ]</code>: reads characters that matches one of the characters
mentioned in the range of characters <code class="code">range</code> (or not mentioned in
it, if the range starts with <code class="code">^</code>). Reads a <code class="code">string</code> that can be
empty, if the next input character does not match the range. The set of
characters from <code class="code">c1</code> to <code class="code">c2</code> (inclusively) is denoted by <code class="code">c1-c2</code>.
Hence, <code class="code">%[0-9]</code> returns a string representing a decimal number
or an empty string if no decimal digit is found; similarly,
<code class="code">%[\\048-\\057\\065-\\070]</code> returns a string of hexadecimal digits.
If a closing bracket appears in a range, it must occur as the
first character of the range (or just after the <code class="code">^</code> in case of
range negation); hence <code class="code">[]]</code> matches a <code class="code">]</code> character and
<code class="code">[^]]</code> matches any character that is not <code class="code">]</code>.</li>
<li><code class="code">r</code>: user-defined reader. Takes the next <code class="code">ri</code> formatted input function and
applies it to the scanning buffer <code class="code">ib</code> to read the next argument. The
input function <code class="code">ri</code> must therefore have type <code class="code"><span class="constructor">Scanning</span>.scanbuf <span class="keywordsign">-></span> <span class="keywordsign">'</span>a</code> and
the argument read has type <code class="code"><span class="keywordsign">'</span>a</code>.</li>
<li><code class="code">{ fmt %}</code>: reads a format string argument.
The format string read must have the same type as the format string
specification <code class="code">fmt</code>.
For instance, <code class="code"><span class="string">"%{%i%}"</span></code> reads any format string that can read a value of
type <code class="code">int</code>; hence <code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"fmt:\\\"number is %u\\\""</span> <span class="string">"fmt:%{%i%}"</span></code>
succeeds and returns the format string <code class="code"><span class="string">"number is %u"</span></code>.</li>
<li><code class="code">\( fmt %\)</code>: scanning format substitution.
Reads a format string to replace <code class="code">fmt</code>.
The format string read must have the same type as the format string
specification <code class="code">fmt</code>.
For instance, <code class="code"><span class="string">"%\( %i% \)"</span></code> reads any format string that can read a value
of type <code class="code">int</code>; hence <code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"\\\"%4d\\\"1234.00"</span> <span class="string">"%\(%i%\)"</span></code>
is equivalent to <code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"1234.00"</span> <span class="string">"%4d"</span></code>.</li>
<li><code class="code">l</code>: returns the number of lines read so far.</li>
<li><code class="code">n</code>: returns the number of characters read so far.</li>
<li><code class="code"><span class="constructor">N</span></code> or <code class="code"><span class="constructor">L</span></code>: returns the number of tokens read so far.</li>
<li><code class="code">!</code>: matches the end of input condition.</li>
<li><code class="code">%</code>: matches one <code class="code">%</code> character in the input.</li>
</ul>
Following the <code class="code">%</code> character that introduces a conversion, there may be
the special flag <code class="code">_</code>: the conversion that follows occurs as usual,
but the resulting value is discarded.
For instance, if <code class="code">f</code> is the function <code class="code"><span class="keyword">fun</span> i <span class="keywordsign">-></span> i + 1</code>, then
<code class="code"><span class="constructor">Scanf</span>.sscanf <span class="string">"x = 1"</span> <span class="string">"%_s = %i"</span> f</code> returns <code class="code">2</code>.
<p>
The field width is composed of an optional integer literal
indicating the maximal width of the token to read.
For instance, <code class="code">%6d</code> reads an integer, having at most 6 decimal digits;
<code class="code">%4f</code> reads a float with at most 4 characters; and <code class="code">%8[\\000-\\255]</code>
returns the next 8 characters (or all the characters still available,
if fewer than 8 characters are available in the input).
<p>
Notes:
<p>
<ul>
<li>as mentioned above, a <code class="code">%s</code> convertion always succeeds, even if there is
nothing to read in the input: it simply returns <code class="code"><span class="string">""</span></code>.</li>
</ul>
<ul>
<li>in addition to the relevant digits, <code class="code"><span class="string">'_'</span></code> characters may appear
inside numbers (this is reminiscent to the usual Caml lexical
conventions). If stricter scanning is desired, use the range
conversion facility instead of the number conversions.</li>
</ul>
<ul>
<li>the <code class="code">scanf</code> facility is not intended for heavy duty lexical
analysis and parsing. If it appears not expressive enough for your
needs, several alternative exists: regular expressions (module
<code class="code"><span class="constructor">Str</span></code>), stream parsers, <code class="code">ocamllex</code>-generated lexers,
<code class="code">ocamlyacc</code>-generated parsers.</li>
</ul>
<br>
<br>
<a name="7_Scanningindicationsinformatstrings"></a>
<div class="h7">Scanning indications in format strings</div><br>
<br>
Scanning indications appear just after the string conversions <code class="code">%s</code>
and <code class="code">%[ range ]</code> to delimit the end of the token. A scanning
indication is introduced by a <code class="code">@</code> character, followed by some
constant character <code class="code">c</code>. It means that the string token should end
just before the next matching <code class="code">c</code> (which is skipped). If no <code class="code">c</code>
character is encountered, the string token spreads as much as
possible. For instance, <code class="code"><span class="string">"%s@\t"</span></code> reads a string up to the next
tab character or to the end of input. If a scanning
indication <code class="code">@c</code> does not follow a string conversion, it is treated
as a plain <code class="code">c</code> character.
<p>
Note:
<p>
<ul>
<li>the scanning indications introduce slight differences in the syntax of
<code class="code"><span class="constructor">Scanf</span></code> format strings, compared to those used for the <code class="code"><span class="constructor">Printf</span></code>
module. However, the scanning indications are similar to those used in
the <code class="code"><span class="constructor">Format</span></code> module; hence, when producing formatted text to be scanned
by <code class="code">!<span class="constructor">Scanf</span>.bscanf</code>, it is wise to use printing functions from the
<code class="code"><span class="constructor">Format</span></code> module (or, if you need to use functions from <code class="code"><span class="constructor">Printf</span></code>, banish
or carefully double check the format strings that contain <code class="code"><span class="string">'@'</span></code>
characters).</li>
</ul>
<br>
<br>
<a name="7_Exceptionsduringscanning"></a>
<div class="h7">Exceptions during scanning</div><br>
<br>
Scanners may raise the following exceptions when the input cannot be read
according to the format string:
<p>
<ul>
<li>Raise <code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scan_failure</span></code> if the input does not match the format.</li>
</ul>
<ul>
<li>Raise <code class="code"><span class="constructor">Failure</span></code> if a conversion to a number is not possible.</li>
</ul>
<ul>
<li>Raise <code class="code"><span class="constructor">End_of_file</span></code> if the end of input is encountered while some more
characters are needed to read the current conversion specification.</li>
</ul>
<ul>
<li>Raise <code class="code"><span class="constructor">Invalid_argument</span></code> if the format string is invalid.</li>
</ul>
Note:
<p>
<ul>
<li>as a consequence, scanning a <code class="code">%s</code> conversion never raises exception
<code class="code"><span class="constructor">End_of_file</span></code>: if the end of input is reached the conversion succeeds and
simply returns the characters read so far, or <code class="code"><span class="string">""</span></code> if none were read.</li>
</ul>
<br>
<br>
<a name="6_Specializedformattedinputfunctions"></a>
<h6>Specialized formatted input functions</h6><br>
<pre><span class="keyword">val</span> <a name="VALfscanf"></a>fscanf : <code class="type"><a href="Pervasives.html#TYPEin_channel">in_channel</a> -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info">
Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but reads from the given channel.
<p>
Warning: since all formatted input functions operate from a scanning
buffer, be aware that each <code class="code">fscanf</code> invocation will operate with a
scanning buffer reading from the given channel. This extra level of
bufferization can lead to strange scanning behaviour if you use low level
primitives on the channel (reading characters, seeking the reading
position, and so on).
<p>
As a consequence, never mixt direct low level reading and high level
scanning from the same input channel.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALsscanf"></a>sscanf : <code class="type">string -> ('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info">
Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but reads from the given string.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALscanf"></a>scanf : <code class="type">('a, 'b, 'c, 'd) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info">
Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but reads from the predefined scanning
buffer <a href="Scanf.Scanning.html#VALstdib"><code class="code"><span class="constructor">Scanf</span>.<span class="constructor">Scanning</span>.stdib</code></a> that is connected to <code class="code">stdin</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALkscanf"></a>kscanf : <code class="type"><a href="Scanf.Scanning.html#TYPEscanbuf">Scanning.scanbuf</a> -><br> (<a href="Scanf.Scanning.html#TYPEscanbuf">Scanning.scanbuf</a> -> exn -> 'a) -> ('b, 'c, 'd, 'a) <a href="Scanf.html#TYPEscanner">scanner</a></code></pre><div class="info">
Same as <a href="Scanf.html#VALbscanf"><code class="code"><span class="constructor">Scanf</span>.bscanf</code></a>, but takes an additional function argument
<code class="code">ef</code> that is called in case of error: if the scanning process or
some conversion fails, the scanning function aborts and calls the
error handling function <code class="code">ef</code> with the scanning buffer and the
exception that aborted the scanning process.<br>
</div>
<br>
<a name="6_Readingformatstringsfrominput"></a>
<h6>Reading format strings from input</h6><br>
<pre><span class="keyword">val</span> <a name="VALbscanf_format"></a>bscanf_format : <code class="type"><a href="Scanf.Scanning.html#TYPEscanbuf">Scanning.scanbuf</a> -><br> ('a, 'b, 'c, 'd, 'e, 'f) format6 -><br> (('a, 'b, 'c, 'd, 'e, 'f) format6 -> 'g) -> 'g</code></pre><div class="info">
<code class="code">bscanf_format ib fmt f</code> reads a format string token from the scannning
buffer <code class="code">ib</code>, according to the given format string <code class="code">fmt</code>, and applies <code class="code">f</code> to
the resulting format string value.
Raise <code class="code"><span class="constructor">Scan_failure</span></code> if the format string value read does not have the
same type as <code class="code">fmt</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALsscanf_format"></a>sscanf_format : <code class="type">string -><br> ('a, 'b, 'c, 'd, 'e, 'f) format6 -><br> (('a, 'b, 'c, 'd, 'e, 'f) format6 -> 'g) -> 'g</code></pre><div class="info">
Same as <a href="Scanf.html#VALbscanf_format"><code class="code"><span class="constructor">Scanf</span>.bscanf_format</code></a>, but reads from the given string.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALformat_from_string"></a>format_from_string : <code class="type">string -><br> ('a, 'b, 'c, 'd, 'e, 'f) format6 -> ('a, 'b, 'c, 'd, 'e, 'f) format6</code></pre><div class="info">
<code class="code">format_from_string s fmt</code> converts a string argument to a format string,
according to the given format string <code class="code">fmt</code>.
Raise <code class="code"><span class="constructor">Scan_failure</span></code> if <code class="code">s</code>, considered as a format string, does not
have the same type as <code class="code">fmt</code>.<br>
</div>
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