or"></a><code><span><span class="keyword">val</span> fold_map : 
  <span><a href="#type-t">t</a> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">init</span>:<span class="type-var">'acc</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">f</span>:<span>(<span><span class="type-var">'acc</span> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-key">key</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-value">value</a> <span c