t;</span></span> bool</span></code></div></div><div class="odoc-spec"><div class="spec value" id="val-sub_join" class="anchored"><a href="#val-sub_join" class="anchor"></a><code><span><span class="keyword">val</span> sub_join : <span><a href="#type-subst">subst</a> <span class="arrow">&#45;&gt;</span></span> <span><a href="#type-subst">subst</a> <span class="arrow">&#45;&gt;</span></span> <a href="#type-subst">subst</a></span></code></div><div class="spec-doc"><p>Compute the common id-exp part of two inputs