an> eval_fun : string <span>&#45;&gt;</span> <span><a href="index.html#type-t">t</a> list</span> <span>&#45;&gt;</span> <span><a href="index.html#type-t">t</a> option</span></code></dt><dt class="spec value" id="val-to_float_range"><a href="#val-to_float_range" class="anchor"></a><code><span class="keyword">val</span> to_float_range : <span>(<span>(<span class="type-var">'a</span> * <a href="B/index.html#type-t">B.t</a>)</span> * <span>(<span class="type-var">'b</span> * <a href="B/index.html#type-t">B.t</a