std::abs, std::labs, std::llabs, std::imaxabs

int       abs( int num );

long      abs( long num );

long long abs( long long num );

long       labs( long num );

long long llabs( long long num );

std::intmax_t abs( std::intmax_t num );

std::intmax_t imaxabs( std::intmax_t num );

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.

Parameters

Return value

The absolute value of num (i.e. |num|), if it is representable.

Notes

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.

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
}

abs(+3) = +3
abs(-3) = +3

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also