idator input =
  let open Validator in
  build build_valid
  |&gt; validate input.hobbies (list_has_min_length 2 &quot;Min 2 hobbies&quot;)</code></pre></dd></dl><dl><dt class="spec value" id="val-list_every"><a href="#val-list_every" class="anchor"></a><code><span class="keyword">val</span> list_every : <span><span>(<span class="type-var">'i</span>, <span class="type-var">'o</span>, <span class="type-var">'err</span>)</span> <a href="index.html#type-validator">validator</a></span> <span>&#45;&gt;</span> 