l</code>.</p></dd></dl><dl><dt class="spec value" id="val-opt_cons"><a href="#val-opt_cons" class="anchor"></a><code><span class="keyword">val</span> opt_cons : <span><span class="type-var">'a</span> option</span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> list</span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> list</span></code></dt><dd><p><code>opt_cons None l</code> returns <code>l</code>. <code>opt_cons (Some x) l</code> returns <code>x :: l</code></p></dd></dl><dl><