std::abs(float),std::fabs,std::fabsf,std::fabsl (3) - Linux Manuals

std::abs(float),std::fabs,std::fabsf,std::fabsl: std::abs(float),std::fabs,std::fabsf,std::fabsl


std::abs(float),std::fabs,std::fabsf,std::fabsl - std::abs(float),std::fabs,std::fabsf,std::fabsl


Defined in header <cmath>
Defined in header <cstdlib> (since C++17)
float abs( float arg ); (1)
double abs( double arg ); (2)
long double abs( long double arg ); (3)
Defined in header <cmath>
float fabs ( float arg );
float fabsf( float arg ); (since C++11)
double fabs ( double arg ); (4) (5)
long double fabs ( long double arg );
long double fabsl( long double arg ); (6) (since C++11)
double fabs ( IntegralType arg ); (7) (since C++11)

1-6) Computes the absolute value of a floating point value arg.
7) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to (5) (the argument is cast to double).

For integral arguments, the_integral_overloads_of_std::abs are likely better matches. If std::abs is called with an argument of type X such that std::is_unsigned<X>::value is true and X cannot be converted to int by integral_promotion, the program is ill-formed. (since C++17)


arg - Value of a floating-point or Integral_type

Return value

If successful, returns the absolute value of arg (|arg|). The value returned is exact and does not depend on any rounding modes.

Error handling

This function is not subject to any of the error conditions specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),

* If the argument is ±0, +0 is returned
* If the argument is ±∞, +∞ is returned
* If the argument is NaN, NaN is returned


// Run this code

  #include <iostream>
  #include <cmath>

  int main()
      std::cout << "abs(+3.0) = " << std::abs(+3.0) << '\n'
                << "abs(-3.0) = " << std::abs(-3.0) << '\n';
      // special values
      std::cout << "abs(-0.0) = " << std::abs(-0.0) << '\n'
                << "abs(-Inf) = " << std::abs(-INFINITY) << '\n';

Possible output:

  abs(+3.0) = 3
  abs(-3.0) = 3
  abs(-0.0) = 0
  abs(-Inf) = inf

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_2735 C++11 std::abs was erroneously required to have overloads for integer types returning double removed the requirement

See also

llabs computes absolute value of an integral value (|x|)


copysignl copies the sign of a floating point value

signbit checks if the given number is negative
                   returns the magnitude of a complex number
abs(std::complex) (function template)
                   applies the function std::abs to each element of valarray
abs(std::valarray) (function template)