/span> )</span> <span class="arrow">&#45;&gt;</span></span> <span class="type-var">'a</span></span></code></div><div class="spec-doc"><p><code>mk_with_id i s f</code> applies <code>f</code> to <code>i</code> is <code>i &lt; 0</code>, otherwise creates a fresh id, reigsters the name <code>s</code> to that fresh id, and returns the result of applying <code>f</code> to that fresh id.</p></div></div><div class="odoc-spec"><div class="spec value" id="val-get_exn" class="anchored"><a href="#val-get_exn" class="an