an> to_bexpr : <a href="../../Csp/index.html#type-var">Csp.var</a> <span>&#45;&gt;</span> <a href="index.html#type-t">t</a> <span>&#45;&gt;</span> <span><span>(<a href="../../Csp/index.html#type-expr">Csp.expr</a> * <a href="../../Csp/index.html#type-cmpop">Csp.cmpop</a> * <a href="../../Csp/index.html#type-expr">Csp.expr</a>)</span> <a href="../../Csp/index.html#type-boolean">Csp.boolean</a></span></code></dt><dt class="spec value" id="val-join"><a href="#val-join" class="anchor"></a><code><span class="key