visitUnaryExpr method
Implementation
@override
Object? visitUnaryExpr(Unary expr) {
final right = _evaluate(expr.right);
switch (expr.operator.type) {
case TokenType.bang:
return !_isTruthy(right);
case TokenType.minus:
_checkNumberOperand(expr.operator, right);
return -(right as double);
default:
return null;
}
}