ables.</p>
<p>The assignment statement in the previous paragraph generates
C++ code that is similar to that generated by the following
sampling statement.</p>
<pre><code>y ~ exponential(lambda);</code></pre>
<p>There are two notable differences. First, the sampling statement will
check the inputs to make sure both <code>lambda</code> is positive and
<code>y</code> is non-negative (which includes checking that neither is the
special not-a-number value).</p>
<p>The second difference is that if <code>lambda</c