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