span> <span class="type-var">'a</span>)</span></span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> option</span></code></dt><dt class="spec value" id="val-reduce_balanced"><a href="#val-reduce_balanced" class="anchor"></a><code><span class="keyword">val</span> reduce_balanced : <span><span class="type-var">'a</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> <span>f:<span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span class="type-var">'a</span> <span>&#4