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<link title="Weak" rel="Chapter" href="Weak.html"><title>Printf</title>
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<center><h1>Module <a href="type_Printf.html">Printf</a></h1></center>
<br>
<pre><span class="keyword">module</span> Printf: <code class="code"><span class="keyword">sig</span></code> <a href="Printf.html">..</a> <code class="code"><span class="keyword">end</span></code></pre>Formatted output functions.<br>
<hr width="100%">
<pre><span class="keyword">val</span> <a name="VALfprintf"></a>fprintf : <code class="type"><a href="Pervasives.html#TYPEout_channel">out_channel</a> -><br> ('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info">
<code class="code">fprintf outchan format arg1 ... argN</code> formats the arguments
<code class="code">arg1</code> to <code class="code">argN</code> according to the format string <code class="code">format</code>, and
outputs the resulting string on the channel <code class="code">outchan</code>.
<p>
The format is a character string which contains two types of
objects: plain characters, which are simply copied to the output
channel, and conversion specifications, each of which causes
conversion and printing of arguments.
<p>
Conversion specifications have the following form:
<p>
<code class="code">% [flags] [width] [.precision] <span class="keyword">type</span></code>
<p>
In short, a conversion specification consists in the <code class="code">%</code> character,
followed by optional modifiers and a type which is made of one or
two characters. The types and their meanings are:
<p>
<ul>
<li><code class="code">d</code>, <code class="code">i</code>, <code class="code">n</code>, <code class="code">l</code>, <code class="code"><span class="constructor">L</span></code>, or <code class="code"><span class="constructor">N</span></code>: convert an integer argument to
signed decimal.</li>
<li><code class="code">u</code>: convert an integer argument to unsigned decimal.</li>
<li><code class="code">x</code>: convert an integer argument to unsigned hexadecimal,
using lowercase letters.</li>
<li><code class="code"><span class="constructor">X</span></code>: convert an integer argument to unsigned hexadecimal,
using uppercase letters.</li>
<li><code class="code">o</code>: convert an integer argument to unsigned octal.</li>
<li><code class="code">s</code>: insert a string argument.</li>
<li><code class="code"><span class="constructor">S</span></code>: insert a string argument in Caml syntax (double quotes, escapes).</li>
<li><code class="code">c</code>: insert a character argument.</li>
<li><code class="code"><span class="constructor">C</span></code>: insert a character argument in Caml syntax (single quotes, escapes).</li>
<li><code class="code">f</code>: convert a floating-point argument to decimal notation,
in the style <code class="code">dddd.ddd</code>.</li>
<li><code class="code"><span class="constructor">F</span></code>: convert a floating-point argument to Caml syntax (<code class="code">dddd.</code>
or <code class="code">dddd.ddd</code> or <code class="code">d.ddd e+-dd</code>).</li>
<li><code class="code">e</code> or <code class="code"><span class="constructor">E</span></code>: convert a floating-point argument to decimal notation,
in the style <code class="code">d.ddd e+-dd</code> (mantissa and exponent).</li>
<li><code class="code">g</code> or <code class="code"><span class="constructor">G</span></code>: convert a floating-point argument to decimal notation,
in style <code class="code">f</code> or <code class="code">e</code>, <code class="code"><span class="constructor">E</span></code> (whichever is more compact).</li>
<li><code class="code"><span class="constructor">B</span></code>: convert a boolean argument to the string <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>: convert 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>: convert 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>: convert 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>: convert an <code class="code">int64</code> argument to
the format specified by the second letter.</li>
<li><code class="code">a</code>: user-defined printer. Takes two arguments and applies the
first one to <code class="code">outchan</code> (the current output channel) and to the
second argument. The first argument must therefore have type
<code class="code">out_channel <span class="keywordsign">-></span> <span class="keywordsign">'</span>b <span class="keywordsign">-></span> unit</code> and the second <code class="code"><span class="keywordsign">'</span>b</code>.
The output produced by the function is inserted in the output of
<code class="code">fprintf</code> at the current point.</li>
<li><code class="code">t</code>: same as <code class="code">%a</code>, but takes only one argument (with type
<code class="code">out_channel <span class="keywordsign">-></span> unit</code>) and apply it to <code class="code">outchan</code>.</li>
<li><code class="code">{ fmt %}</code>: convert a format string argument. The argument must
have the same type as the internal format string <code class="code">fmt</code>.</li>
<li><code class="code">( fmt %)</code>: format string substitution. Takes a format string
argument and substitutes it to the internal format string <code class="code">fmt</code>
to print following arguments. The argument must have the same
type as <code class="code">fmt</code>.</li>
<li><code class="code">!</code>: take no argument and flush the output.</li>
<li><code class="code">%</code>: take no argument and output one <code class="code">%</code> character.</li>
</ul>
The optional <code class="code">flags</code> are:<ul>
<li><code class="code">-</code>: left-justify the output (default is right justification).</li>
<li><code class="code">0</code>: for numerical conversions, pad with zeroes instead of spaces.</li>
<li><code class="code">+</code>: for numerical conversions, prefix number with a <code class="code">+</code> sign if positive.</li>
<li>space: for numerical conversions, prefix number with a space if positive.</li>
<li><code class="code"><span class="keywordsign">#</span></code>: request an alternate formatting style for numbers.</li>
</ul>
The optional <code class="code">width</code> is an integer indicating the minimal
width of the result. For instance, <code class="code">%6d</code> prints an integer,
prefixing it with spaces to fill at least 6 characters.
<p>
The optional <code class="code">precision</code> is a dot <code class="code">.</code> followed by an integer
indicating how many digits follow the decimal point in the <code class="code">%f</code>,
<code class="code">%e</code>, and <code class="code">%<span class="constructor">E</span></code> conversions. For instance, <code class="code">%.4f</code> prints a <code class="code">float</code> with
4 fractional digits.
<p>
The integer in a <code class="code">width</code> or <code class="code">precision</code> can also be specified as
<code class="code">*</code>, in which case an extra integer argument is taken to specify
the corresponding <code class="code">width</code> or <code class="code">precision</code>. This integer argument
precedes immediately the argument to print.
For instance, <code class="code">%.*f</code> prints a <code class="code">float</code> with as many fractional
digits as the value of the argument given before the float.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALprintf"></a>printf : <code class="type">('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info">
Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but output on <code class="code">stdout</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALeprintf"></a>eprintf : <code class="type">('a, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info">
Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but output on <code class="code">stderr</code>.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALifprintf"></a>ifprintf : <code class="type">'a -> ('b, 'a, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'b</code></pre><div class="info">
Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but does not print anything.
Useful to ignore some material when conditionally printing.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALsprintf"></a>sprintf : <code class="type">('a, unit, string) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info">
Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but instead of printing on an output channel,
return a string containing the result of formatting the arguments.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALbprintf"></a>bprintf : <code class="type"><a href="Buffer.html#TYPEt">Buffer.t</a> -> ('a, <a href="Buffer.html#TYPEt">Buffer.t</a>, unit) <a href="Pervasives.html#TYPEformat">format</a> -> 'a</code></pre><div class="info">
Same as <a href="Printf.html#VALfprintf"><code class="code"><span class="constructor">Printf</span>.fprintf</code></a>, but instead of printing on an output channel,
append the formatted arguments to the given extensible buffer
(see module <a href="Buffer.html"><code class="code"><span class="constructor">Buffer</span></code></a>).<br>
</div>
<br>
Formatted output functions with continuations.<br>
<pre><span class="keyword">val</span> <a name="VALkfprintf"></a>kfprintf : <code class="type">(<a href="Pervasives.html#TYPEout_channel">out_channel</a> -> 'a) -><br> <a href="Pervasives.html#TYPEout_channel">out_channel</a> -><br> ('b, <a href="Pervasives.html#TYPEout_channel">out_channel</a>, unit, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info">
Same as <code class="code">fprintf</code>, but instead of returning immediately,
passes the out channel to its first argument at the end of printing.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALksprintf"></a>ksprintf : <code class="type">(string -> 'a) -> ('b, unit, string, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info">
Same as <code class="code">sprintf</code> above, but instead of returning the string,
passes it to the first argument.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALkbprintf"></a>kbprintf : <code class="type">(<a href="Buffer.html#TYPEt">Buffer.t</a> -> 'a) -><br> <a href="Buffer.html#TYPEt">Buffer.t</a> -> ('b, <a href="Buffer.html#TYPEt">Buffer.t</a>, unit, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info">
Same as <code class="code">bprintf</code>, but instead of returning immediately,
passes the buffer to its first argument at the end of printing.<br>
</div>
<pre><span class="keyword">val</span> <a name="VALkprintf"></a>kprintf : <code class="type">(string -> 'a) -> ('b, unit, string, 'a) <a href="Pervasives.html#TYPEformat4">format4</a> -> 'b</code></pre><div class="info">
A deprecated synonym for <code class="code">ksprintf</code>.<br>
</div>
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