int abs( int num );
(1) (constexpr since C++23)long abs( long num );
(2) (constexpr since C++23)long long abs( long long num );
(3) (since C++11)long labs( long num );
(4) (constexpr since C++23)long long llabs( long long num );
(5) (since C++11)Computes the absolute value of the integer number num. The behavior is undefined if the result cannot be represented by the return type.
If std::abs
is called with an unsigned integral argument that cannot be converted to int by integral promotion, the program is ill-formed.
The absolute value of num (i.e. |num|
), if it is representable.
In 2's complement systems, the absolute value of the most-negative value is out of range, e.g. for 32-bit 2's complement type int, INT_MIN is -2147483648, but the would-be result 2147483648 is greater than INT_MAX, which is 2147483647.
[edit] Example#include <climits> #include <cstdlib> #include <iostream> int main() { std::cout << std::showpos << "abs(+3) = " << std::abs(3) << '\n' << "abs(-3) = " << std::abs(-3) << '\n'; // std::cout << std::abs(INT_MIN); // undefined behavior on 2's complement systems }
Output:
abs(+3) = +3 abs(-3) = +3[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 2192 C++98 overloads ofstd::abs
were
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