/*@NotNull*/
public Expression optimize(
/*@NotNull*/ ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
throws XPathException {
Expression e2 = super.optimize(visitor, contextItemType);
if (e2 != this) {
return e2;
}
// See if we can deduce the answer from the cardinality
int c = argument[0].getCardinality();
if (c == StaticProperty.ALLOWS_ONE_OR_MORE) {
return new Literal(BooleanValue.FALSE);
} else if (c == StaticProperty.ALLOWS_ZERO) {
return new Literal(BooleanValue.TRUE);
}
// Rewrite
// empty(A|B) => empty(A) and empty(B)
if (argument[0] instanceof VennExpression) {
VennExpression v = (VennExpression) argument[0];
if (v.getOperator() == Token.UNION && !visitor.isOptimizeForStreaming()) {
FunctionCall e0 =
SystemFunction.makeSystemFunction("empty", new Expression[] {v.getOperands()[0]});
FunctionCall e1 =
SystemFunction.makeSystemFunction("empty", new Expression[] {v.getOperands()[1]});
return new AndExpression(e0, e1).optimize(visitor, contextItemType);
}
}
return this;
}
/**
* Return the negation of the expression
*
* @return the negation of the expression
*/
public Expression negate() {
FunctionCall fc = SystemFunction.makeSystemFunction("exists", getArguments());
fc.setLocationId(getLocationId());
return fc;
}