In C++20 the way that the relational operators work was changed, notably with the introduction of the spaceship <=> operator. In particular, If you only provide operator==, then a != b is rewritten to !(a == b). From [over.match.oper]/3.4: The rewritten candidate set is determined as follows: For the relational ([expr.rel]) operators, the rewritten candidates … Read more
In C++, structs do not have a comparison operator generated by default. You need to write your own: bool operator==(const MyStruct1& lhs, const MyStruct1& rhs) { return /* your comparison code goes here */ }
No, there is not. To overload operator==, you must provide a user-defined type as one of the operands and a pointer (either AString* or const char*) does not qualify. And when comparing two pointers, the compiler has a very adequate built-in operator==, so it will not consider converting one of the arguments to a class … Read more
Operator precedence 2.x, 3.x. The precedence of not is lower than that of in. So it is equivalent to: >>> not ((True) in [False, True]) False This is what you want: >>> (not True) in [False, True] True As @Ben points out: It’s recommended to never write not(True), prefer not True. The former makes it … Read more
Because == (and ===) test to see if two objects are the same object and not if they are identical objects. Most test frameworks will include functions such as deepEqual if you want to see if two objects are identical.
” == ‘0’ // false The left hand side is an empty string, and the right hand side is a string with one character. They are false because it is making a comparison between two un identical strings (thanks Niall). 0 == ” // true Hence, why this one is true, because 0 is falsy … Read more
I’d like to do it all by myself.. You should only compare the values of Obj::field2 if the values of Obj::field1 are equal. The easy-to-understand way: /* This will meet the requirements of Strict-Weak-Ordering */ if (a.field1 != b.field1) return a.field1 < b.field1; else return a.field2 < b.field2; The correct (recommended) way: The “correct” way … Read more
$a === $b (Identical) TRUE if $a is equal to $b, and they are of the same type. (introduced in PHP 4) PHP Docs
From the SymPy documentation == represents exact structural equality testing. “Exact” here means that two expressions will compare equal with == only if they are exactly equal structurally. Here, (x+1)^2 and x^2+2x+1 are not the same symbolically. One is the power of an addition of two terms, and the other is the addition of three … Read more
Yes. Any operators classified as comparisons can be chained. From the language reference: Formally, if a, b, c, …, y, z are expressions and op1, op2, …, opN are comparison operators, then a op1 b op2 c … y opN z is equivalent to a op1 b and b op2 c and … y opN … Read more