ction.html#variables.section">section on variables</a> for more
information on valid identifiers. For example,</p>
<pre class="stan"><code>real foo(real mu, real sigma);</code></pre>
<p>declares a function named <code>foo</code> with two argument variables of
types <code>real</code> and <code>real</code>. The arguments are named <code>mu</code>
and <code>sigma</code>, but that is not part of the declaration. Two
user-defined functions may <em>not</em> have the same name even if they have
different sequences