span><span>(<span class="type-var">'a</span>, <span class="type-var">'x</span>)</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> </span><span class="arg"><span>(<span class="arg"><span class="type-var">'a</span> <span>&#45;&gt;</span> </span><span><span>(<span class="type-var">'b</span>, <span class="type-var">'x</span>)</span> <a href="index.html#type-t">t</a></span>)</span> <span>&#45;&gt;</span> </span><span><span>(<span class="type-var">'b</span>, <span class="type-var">'x</span