an><span class="type-var">'a</span> <span class="arrow">&#45;&gt;</span></span> <span><span class="type-var">'b</span> <span class="arrow">&#45;&gt;</span></span> unit)</span> <span class="arrow">&#45;&gt;</span></span> unit</span></code></div><div class="spec-doc"><p>Like <code>Option.iter</code> but gets two parameters.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-map_changed"><a href="#val-map_changed" class="anchor"></a><code><span><span class="keyword">val</span> map_c