> <span class="type-var">'b</span></span></code></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-value_map_f"><a href="#val-value_map_f" class="anchor"></a><code><span><span class="keyword">val</span> value_map_f : <span><span><span>(<span class="type-var">_</span>, <span class="type-var">'a</span>)</span> <a href="#type-t">t</a></span> <span class="arrow">&#45;&gt;</span></span> <span><span class="label">default</span>:<span>(<span>unit <span class="arrow">&#45;&gt;</span></span>