code: public static ExprBoolean toExprBoolean(Expression left, Expression right, int operation) {
  	if (left instanceof Literal && right instanceof Literal) {
  	    Boolean l = ((Literal) left).getBoolean(null);
  	    Boolean r = ((Literal) right).getBoolean(null);
  
  	    if (l != null && r != null) {
  		switch (operation) {
  		case Factory.OP_BOOL_AND:
  		    return left.getFactory().createLitBoolean(l.booleanValue() && r.booleanValue(), left.getStart(), right.getEnd());
  		case Factory.OP_BOOL_OR:
  		    return left.getFactory().createLitBoolean(l.booleanValue() || r.booleanValue(), left.getStart(), right.getEnd());
  		case Factory.OP_BOOL_XOR:
  		    return left.getFactory().createLitBoolean(l.booleanValue() ^ r.booleanValue(), left.getStart(), right.getEnd());
  		}
  	    }
  	}
  	return new OpBool(left, right, operation);
      }
docs: Create a String expression from a Expression
  
  @param left
  @param right
  
  @return String expression
  @throws TemplateException