/usr/lib/swi-prolog/doc/Manual/miscarith.html

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<h2 id="sec:miscarith"><a id="sec:4.28"><span class="sec-nr">4.28</span> <span class="sec-title">Misc 
arithmetic support predicates</span></a></h2>

<a id="sec:miscarith"></a>

<dl class="latex">
<dt class="pubdef"><a id="set_random/1"><strong>set_random</strong>(<var>+Option</var>)</a></dt>
<dd class="defbody">
Controls the random number generator accessible through the
<em>functions</em> <a class="function" href="arith.html#f-random/1">random/1</a> 
and <a class="function" href="arith.html#f-random_float/0">random_float/0</a>. 
Note that the library <code>library(random)</code> provides an 
alternative API to the same random primitives.

<dl class="latex">
<dt><strong>seed</strong>(<var>+Seed</var>)</dt>
<dd class="defbody">
Set the seed of the random generator for this thread. <var>Seed</var> is 
an integer or the atom <code>random</code>. If <code>random</code>, 
repeat the initialization procedure described with the function
<a class="function" href="arith.html#f-random/1">random/1</a>. Here is 
an example:

<pre class="code">
?- set_random(seed(111)), A is random(6).
A = 5.
?- set_random(seed(111)), A is random(6).
A = 5.
</pre>

</dd>
<dt><strong>state</strong>(<var>+State</var>)</dt>
<dd class="defbody">
Set the generator to a state fetched using the state property of <a id="idx:randomproperty1:1180"></a><a class="pred" href="miscarith.html#random_property/1">random_property/1</a>. 
Using other values may lead to undefined behaviour.<sup class="fn">85<span class="fn-text">The 
limitations of the underlying (GMP) library are unknown, which makes it 
impossible to validate the <var>State</var>.</span></sup>
</dd>
</dl>

</dd>
<dt class="pubdef"><a id="random_property/1"><strong>random_property</strong>(<var>?Option</var>)</a></dt>
<dd class="defbody">
True when <var>Option</var> is a current property of the random 
generator. Currently, this predicate provides access to the state. This 
predicate is not present on systems where the state is inaccessible.

<dl class="latex">
<dt><strong>state</strong>(<var>-State</var>)</dt>
<dd class="defbody">
Describes the current state of the random generator. State is a normal 
Prolog term that can be asserted or written to a file. Applications 
should make no other assumptions about its representation. The only 
meaningful operation is to use as argument to <a id="idx:setrandom1:1181"></a><a class="pred" href="miscarith.html#set_random/1">set_random/1</a> 
using the
<code>state(State)</code> option.<sup class="fn">bug<span class="fn-text">GMP 
provides no portable mechanism to fetch and restore the state. The 
current implementation works, but the state depends on the platform. 
I.e., it is generally not possible to reuse the state with another 
version of GMP or on a CPU with different datasizes or endian-ness.</span></sup>
</dd>
</dl>

</dd>
<dt class="pubdef"><a id="current_arithmetic_function/1"><strong>current_arithmetic_function</strong>(<var>?Head</var>)</a></dt>
<dd class="defbody">
True when <var>Head</var> is an evaluable function. For example:

<pre class="code">
?- current_arithmetic_function(sin(_)).
true.
</pre>

<p></dd>
</dl>

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swi-prolog-nox 6.6.4-2ubuntu1 / usr / lib / swi-prolog / doc / Manual / miscarith.html
