 <span><span class="type-var">'a</span> <a href="index.html#type-check">check</a></span> <span>&#45;&gt;</span> <span><span><span class="type-var">'a</span> list</span> <a href="index.html#type-check">check</a></span></code></dt><dt class="spec value" id="val-tuple"><a href="#val-tuple" class="anchor"></a><code><span class="keyword">val</span> tuple : <span><span class="type-var">'a</span> <a href="index.html#type-check">check</a></span> <span>&#45;&gt;</span> <span><span class="type-var">'b</span> <a href=