is interpreted as
<code>y + (log(x))</code>.</p>
<div id="type-signatures-and-result-type-inference" class="section level3 unnumbered">
<h3>Type signatures and result type inference</h3>
<p>Each function has a type signature which determines the allowable type
of its arguments and its return type. For instance, the function
signature for the logarithm function can be expressed as</p>
<div class="sourceCode" id="cb121"><pre class="sourceCode stan"><code class="sourceCode stan"><span id="cb121-1"><a href="fun