" class="anchor"></a><code><span class="keyword">val</span> fold_map : <span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> <a href="argument-1-P/index.html#type-t">P.t</a></span>)</span> <span>&#45;&gt;</span> <span>(<span class="type-var">'b</span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> <a href="argument-1-P/index.html#type-t">P.t</a></span>)</span> <span>&#45;&gt;</span> <span><span>(<span class="type-var">'a</span>, <span class="ty