/*
* This file is part of the X10 project (http://x10-lang.org).
*
* This file is licensed to You under the Eclipse Public License (EPL);
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.opensource.org/licenses/eclipse-1.0.php
*
* (C) Copyright IBM Corporation 2006-2010.
*/
package x10.constraint.xnative;
/**
Class representing left == right constraints.
Not treated as an atomic formula.
@author njnystrom
*/
public class XEquals extends XNativeFormula<String> implements x10.constraint.XEquals {
private static final long serialVersionUID = 5003576451176083570L;
public static final String name = "===";
public static final String asExprName = "==";
public XEquals(XNativeTerm left, XNativeTerm right) {
super(name, asExprName, false, left, right);
}
@Override
public XPromise internIntoConstraint(XNativeConstraint c, XPromise last) {
XPromise p = c.intern((XNativeTerm)left());
if (p == null) return null;
XPromise q = c.intern((XNativeTerm)right());
if (q == null) return null;
XNativeTerm pTerm=p.term(),qTerm=q.term();
if (pTerm instanceof XNativeLit && qTerm instanceof XNativeLit) {
return c.intern((XNativeTerm) (p.equals(q) ? XNativeLit.TRUE : XNativeLit.FALSE));
}
else {
if (p == q || p.term().equals(q.term())) // Handle x==x also
return c.intern((XNativeTerm) XNativeLit.TRUE);
else return super.internIntoConstraint(c, last);
}
}
@Override
public String toString() {return left() + "==" + right();}
}