Overload power with correctly in c++?
c++, operator-overloading, operators, xor
Solution
You cannot change the associativity or priority of an operator in C++ by overloading it. These rules are hardwired into the language syntax.
The C++ standard says (§13.5.6, emphasis mine):
An operator function shall either be a non-static member function or be a non-member function and have at least one parameter whose type is a class, a reference to a class, an enumeration, or a reference to an enumeration. It is not possible to change the precedence, grouping, or number of operands of operators. The meaning of the operators =, (unary) &, and , (comma), predefined for each type, can be changed [...]
Not only is the `^` operator left-associative, but it also has a very low precedence. The correct precedence for a power operator should be higher than the multiplication (so priority 4 or better on this table), but it has priority 10--this means that even additions and subtractions are evaluated before it. `1 + 2 ^ 3 * 4` will be parsed as `(1 + 2) ^ (3 * 4)`, while a mathematically correct power operator should parse as `1 + (2 ^ 3) * 4`.
If the associativity or priority of an operator could be modified, a huge, huge syntactical mess would ensue. My humble opinion is that you should not try to overload the `^` operator to use it as a power operator. I would rather make a `power` method on the class.
Problem
In c++ I implemented an `integer` class and I overloaded `operator ^` to be the power function. ``` integer integer::operator^ (const integer& rhs){ return integer(pow(this->.i, rhs.i)); } ``` This is working correctly for two operands. ``` integer i1, i2, i3 ; i4 = i1 ^ i2 ^ i3; ``` The value of `i4` is wrong mathematically because associativity required right-to-left. How can I solve this problem? How do I change associativity? I got reasonable answers and I learn: ``` -We can't change associativity or priority of an operator. -Good is Not to overload operators to do something conceptually different to the built-in versions -Even compiler can't support; it hard to implement! ```