As far as I know there is no such operator in JavaScript but you can use Math.sign() function: Math.sign(a – b); NOTE: As was mentioned in comments, Math.sign() is not currently supported by all browsers. Check for compatibility (MDN).
This is by design. [class.compare.default] (emphasis mine) 3 If the class definition does not explicitly declare an == operator function, but declares a defaulted three-way comparison operator function, an == operator function is declared implicitly with the same access as the three-way comparison operator function. The implicitly-declared == operator for a class X is an … Read more
The basic problem comes from the facts that your type is incoherent and the standard library didn’t call you on it until C++20. That is, your type was always kind of broken, but things were narrowly enough defined that you could get away with it. Your type is broken because its comparison operators make no … Read more
Why must I provide operator== when operator<=> is enough? Well, mainly because it’s not enough 🙂 Equality and ordering are different buckets when it comes time for C++ to rewrite your statements: Equality Ordering Primary == <=> Secondary != <, >, <=, >= Primary operators have the ability to be reversed, and secondary operators have … Read more
The operator solves the problem with numeric overflow that you get with subtraction: if you subtract a large positive number from a negative that is close to INT_MIN, you get a number that cannot be represented as an int, thus causing undefined behavior. Although version 3 is free from this problem, it utterly lacks readability: … Read more
This is by design. [class.compare.default] (emphasis mine) 3 If the class definition does not explicitly declare an == operator function, but declares a defaulted three-way comparison operator function, an == operator function is declared implicitly with the same access as the three-way comparison operator function. The implicitly-declared == operator for a class X is an … Read more
Indeed, C++20 unfortunately makes this code infinitely recursive. Here’s a reduced example: struct F { /*implicit*/ F(int t_) : t(t_) {} // member: #1 bool operator==(F const& o) const { return t == o.t; } // non-member: #2 friend bool operator==(const int& y, const F& x) { return x == y; } private: int t; … Read more
TL;DR It’s the NULL safe equal operator. Like the regular = operator, two values are compared and the result is either 0 (not equal) or 1 (equal); in other words: ‘a’ <=> ‘b’ yields 0 and ‘a’ <=> ‘a’ yields 1. Unlike the regular = operator, values of NULL don’t have a special meaning and … Read more
The <=> (“Spaceship”) operator will offer combined comparison in that it will : Return 0 if values on either side are equal Return 1 if the value on the left is greater Return -1 if the value on the right is greater The rules used by the combined comparison operator are the same as the … Read more
This is called the three-way comparison operator. According to the P0515 paper proposal: There’s a new three-way comparison operator, <=>. The expression a <=> b returns an object that compares <0 if a < b, compares >0 if a > b, and compares ==0 if a and b are equal/equivalent. To write all comparisons for … Read more