 class="optlabel">?var_filter</span>:<span>(<span><a href="../../IR/Var/index.html#type-t">IR.Var.t</a> <span class="arrow">&#45;&gt;</span></span> bool)</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">init</span>:<span class="type-var">'accum</span> <span class="arrow">&#45;&gt;</span></span>
  <span><span class="label">finish</span>:<span>(<span><span class="type-var">'accum</span> <span class="arrow">&#45;&gt;</span></span> <span class="type-var">'final</span>)</span> <span