e-var">'a</span>)</span></span> <span>&#45;&gt;</span> <span>lo:int</span> <span>&#45;&gt;</span> <span>hi:int</span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> list</span></code></dt><dt class="spec value" id="val-flat_map"><a href="#val-flat_map" class="anchor"></a><code><span class="keyword">val</span> flat_map : <span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span><span class="type-var">'b</span> list</span>)</span> <span>&#45;&gt;</span> <span><span class="type-var">'