class="type-var">'a</span>)</span></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>like map, but returns the original list if unchanged</p></dd></dl><dl><dt class="spec value" id="val-filter_changed"><a href="#val-filter_changed" class="anchor"></a><code><span class="keyword">val</span> filter_changed : <span>f:<span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> bool)</span