class="type-var">'next_acc</span>, <span><span class="type-var">'e</span> <a href="index.html#type-errors">errors</a></span>)</span> Stdlib.result</span></code></dt><dd><p>Keep a value as is.</p><pre><code class="ml">let validator input =
  let open Validator in
  build build_valid
  |&gt; keep input.message</code></pre></dd></dl><dl><dt class="spec value" id="val-build"><a href="#val-build" class="anchor"></a><code><span class="keyword">val</span> build : <span>(<span class="type-var">'a</span> <span>&#45