pan> <span class="type-var">'a</span></span></code></div><div class="spec-doc"><p>Like <code>Option.value_exn</code> but raises <code>Caml.Not_found</code> when called with <code>None</code>.</p></div></div><div class="odoc-spec"><div class="spec value anchored" id="val-value_default_f"><a href="#val-value_default_f" class="anchor"></a><code><span><span class="keyword">val</span> value_default_f : <span>f:<span>(<span>unit <span class="arrow">&#45;&gt;</span></span> <span class="type-var">'a</span>)</span> 