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

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<h2 id="sec:gensym"><a id="sec:A.11"><span class="sec-nr">A.11</span> <span class="sec-title">library(gensym): 
Generate unique identifiers</span></a></h2>

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

<p>Gensym (<b>Gen</b>erate <b>Sym</b>bols) is an old library for 
generating unique symbols (atoms). Such symbols are generated from a 
base atom which gets a sequence number appended. Of course there is no 
guarantee that `catch22' is not an already defined atom and therefore 
one must be aware these atoms are only unique in an isolated context.

<p>The SWI-Prolog gensym library is thread-safe. The sequence numbers 
are global over all threads and therefore generated atoms are unique 
over all threads.

<dl class="latex">
<dt class="pubdef"><a id="gensym/2"><strong>gensym</strong>(<var>+Base, 
-Unique</var>)</a></dt>
<dd class="defbody">
Generate a unique atom from base <var>Base</var> and unify it with <var>Unique</var>.
<var>Base</var> should be an atom. The first call will return &lt;<var>base</var>&gt;1 
, the next &lt;<var>base</var>&gt;2 , etc. Note that this is no 
guarantee that the atom is unique in the system.</dd>
<dt class="pubdef"><a id="reset_gensym/1"><strong>reset_gensym</strong>(<var>+Base</var>)</a></dt>
<dd class="defbody">
Restart generation of identifiers from <var>Base</var> at &lt;<var>Base</var>&gt;1. 
Used to make sure a program produces the same results on subsequent 
runs. Use with care.</dd>
<dt class="pubdef"><a id="reset_gensym/0"><strong>reset_gensym</strong></a></dt>
<dd class="defbody">
Reset gensym for all registered keys. This predicate is available for 
compatibility only. New code is strongly advised to avoid the use of 
reset_gensym or at least to reset only the keys used by your program to 
avoid unexpected side effects on other components.
</dd>
</dl>

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