NAME¶

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

Synopsis¶

Defined in header <cstdlib>
Defined in header <cmath>
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)
(constexpr since C++23)
Defined in header <cstdlib>
long labs( long num ); (4) (constexpr since C++23)
long long llabs( long long num ); (5) (since C++11)
(constexpr since C++23)
Defined in header <cinttypes>
std::intmax_t abs( std::intmax_t num ); (6) (since C++11)
(constexpr since C++23)
std::intmax_t imaxabs( std::intmax_t num ); (7) (since C++11)
(constexpr since C++23)

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.

Overload (6) of std::abs for std::intmax_t is provided in <cinttypes> (since C++11)
if and only if std::intmax_t is an extended integer type.

Parameters¶

num - integer value

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¶

// Run this code

#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

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 of std::abs were declared these overloads
inconsistently declared in two headers in both headers

See also¶

abs(float)
fabs
fabsf absolute value of a floating point value (\(\small{|x|}\)|x|)
fabsl (function)
(C++11)
(C++11)
abs(std::complex) returns the magnitude of a complex number
(function template)
abs(std::valarray) applies the function abs to each element of valarray
(function template)
C documentation for
abs,
labs,
llabs