TL;DR: in C++98/03 the clause was not present, and the standard did not specify relational operators for void pointers (core issue 879, see end of this post); the odd clause about comparing void pointers was added in C++11 to resolve it, but this in turn gave rise to two other core issues 583 & 1512 … Read more
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
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
All iterators are equality comparable. Only random access iterators are relationally comparable. Input iterators, forward iterators, and bidirectional iterators are not relationally comparable. Thus, the comparison using != is more generic and flexible than the comparison using <. There are different categories of iterators because not all ranges of elements have the same access properties. … Read more
if ($profitloss < 0) { echo “The profitloss is negative”; } Edit: I feel like this was too simple an answer for the rep so here’s something that you may also find helpful. In PHP we can find the absolute value of an integer by using the abs() function. For example if I were trying … 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 */ }
I believe Python has special case handling for sequences of relational operators to make range comparisons easy to express. It’s much nicer to be able to say 0 < x <= 5 than to say (0 < x) and (x <= 5). These are called chained comparisons. And that’s a link to the documentation for … Read more
TL;DR: The operations are well defined according to the draft C++ standard. Details We can see that by going to the draft C++ standard section 5.9 Relational operators which says (emphasis mine going forward): The operands shall have arithmetic, enumeration, or pointer type, or type std::nullptr_t. The operators < (less than), > (greater than), <= … Read more
Just searched for the docs, and found this: Containment Operator: The in operator performs containment test. It returns true if the left operand is contained in the right: {# returns true #} {{ 1 in [1, 2, 3] }} {{ ‘cd’ in ‘abcde’ }}
The difference is that there is no operator ==!. This expression: $a ==! $b Is basically the same as this: $a == (!$b)