>.
</div>
<div id="calling-functions" class="section level2">
<h2><span class="header-section-number">9.3</span> Calling Functions</h2>
<p>All function arguments are mandatory—there are no default values.</p>
<div id="functions-as-expressions" class="section level3">
<h3>Functions as Expressions</h3>
<p>Functions with non-void return types are called just like any other
built-in function in Stan—they are applied to appropriately typed
arguments to produce an expression, which has a value when executed.<