// This logically inverts a condition expression, simplifying the AST if possible
private static Expression invertCondition(Expression expression) {
if (expression instanceof UnaryExpr) {
final UnaryExpr unary = (UnaryExpr) expression;
// Unary not expression, just remove the not
if (unary.getOperator() == UnaryExpr.Operator.not) {
return unary.getExpr();
} else {
// Else wrap it in a not
return new UnaryExpr(expression, UnaryExpr.Operator.not);
}
} else if (expression instanceof BinaryExpr) {
final BinaryExpr binary = (BinaryExpr) expression;
final Operator inverted;
// For binary compare operators, just use the opposite operator
// Boolean operators use De Morgan's law
// Other operators use a not operator, but are also enclosed in ()
switch (binary.getOperator()) {
case equals:
inverted = Operator.notEquals;
break;
case notEquals:
inverted = Operator.equals;
break;
case less:
inverted = Operator.greaterEquals;
break;
case greater:
inverted = Operator.lessEquals;
break;
case lessEquals:
inverted = Operator.greater;
break;
case greaterEquals:
inverted = Operator.less;
break;
case or:
return new BinaryExpr(
invertCondition(binary.getLeft()), invertCondition(binary.getRight()), Operator.and);
case and:
return new BinaryExpr(
invertCondition(binary.getLeft()), invertCondition(binary.getRight()), Operator.or);
default:
return new UnaryExpr(new EnclosedExpr(binary), UnaryExpr.Operator.not);
}
return new BinaryExpr(binary.getLeft(), binary.getRight(), inverted);
} else if (expression instanceof AssignExpr
|| expression instanceof ConditionalExpr
|| expression instanceof InstanceOfExpr) {
// This expressions have lower precedence so they need to be enclosed in ()
return new UnaryExpr(new EnclosedExpr(expression), UnaryExpr.Operator.not);
} else {
// These are higher precedence, no need for ()
return new UnaryExpr(expression, UnaryExpr.Operator.not);
}
}
@Override
public Boolean visit(final BinaryExpr n1, final Node arg) {
final BinaryExpr n2 = (BinaryExpr) arg;
if (n1.getOperator() != n2.getOperator()) {
return Boolean.FALSE;
}
if (!nodeEquals(n1.getLeft(), n2.getLeft())) {
return Boolean.FALSE;
}
if (!nodeEquals(n1.getRight(), n2.getRight())) {
return Boolean.FALSE;
}
return Boolean.TRUE;
}
@Override
public void visit(final BinaryExpr n, final A arg) {
visitComment(n.getComment(), arg);
n.getLeft().accept(this, arg);
n.getRight().accept(this, arg);
}