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<a name="The-Random-Number-Generator-Interface"></a>
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<p>
Next: <a href="Random-number-generator-initialization.html#Random-number-generator-initialization" accesskey="n" rel="next">Random number generator initialization</a>, Previous: <a href="General-comments-on-random-numbers.html#General-comments-on-random-numbers" accesskey="p" rel="previous">General comments on random numbers</a>, Up: <a href="Random-Number-Generation.html#Random-Number-Generation" accesskey="u" rel="up">Random Number Generation</a> &nbsp; [<a href="Function-Index.html#Function-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="The-Random-Number-Generator-Interface-1"></a>
<h3 class="section">18.2 The Random Number Generator Interface</h3>

<p>It is important to remember that a random number generator is not a
&ldquo;real&rdquo; function like sine or cosine.  Unlike real functions, successive
calls to a random number generator yield different return values.  Of
course that is just what you want for a random number generator, but to
achieve this effect, the generator must keep track of some kind of
&ldquo;state&rdquo; variable.  Sometimes this state is just an integer (sometimes
just the value of the previously generated random number), but often it
is more complicated than that and may involve a whole array of numbers,
possibly with some indices thrown in.  To use the random number
generators, you do not need to know the details of what comprises the
state, and besides that varies from algorithm to algorithm.
</p>
<a name="index-gsl_005frng_005ftype"></a>
<p>The random number generator library uses two special structs,
<code>gsl_rng_type</code> which holds static information about each type of
generator and <code>gsl_rng</code> which describes an instance of a generator
created from a given <code>gsl_rng_type</code>.
</p>
<p>The functions described in this section are declared in the header file
<samp>gsl_rng.h</samp>.
</p>



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