<span class="keyword">val</span>&nbsp;mapU&nbsp;:<br>
&nbsp;&nbsp;&nbsp;&nbsp;<span class="keywordsign">'</span>a&nbsp;<span class="constructor">Belt_MutableQueue</span>.t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;(<span class="keywordsign">'</span>a&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="keywordsign">'</span>b&nbsp;[@bs])&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="keywordsign">'</span>b&nbsp;<span class="constructor">Belt_MutableQueue</span>.t<br>
&nbsp;&nbs