std::abs(float),std::fabs,std::fabsf,std::fabsl(3)

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

Synopsis
   Defined in header <cmath>
   Defined in header <cstdlib>
   float abs( float num );
   double abs( double num ); (until C++23)
   long double abs( long double num );
   constexpr /* floating-point-type */
               abs( /* floating-point-type */ (since C++23)
   num );
   Defined in header <cmath>
   float fabs ( float num );
   double fabs ( double num ); (until C++23)
   long double fabs ( long double num ); (1)
   constexpr /* floating-point-type */
               fabs ( /* floating-point-type */ (since C++23)
   num );
                        (since C++11)
   float fabsf( float num ); (2) (3) (constexpr since
                        C++23)
                        (since C++11)
   long double fabsl( long double num ); (4) (constexpr since
                        C++23)
   Additional overloads (since C++11)
   Defined in header <cmath>
   template< class Integer > (since C++11)
   double fabs ( Integer num ); (A) (constexpr since
                        C++23)
   1-4) Computes the absolute value of the floating-point value num.
   The library provides overloads of std::abs and std::fabs for all cv-unqualified
   floating-point types as the type of the parameter num.
   (since C++23)
   A) Additional overloads are provided for all integer types, which are (since C++11)
   treated as double.
   For integral arguments, the integral overloads of std::abs are likely better
   matches. 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
   num - floating-point or integer value

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.

Notes
   The additional overloads are not required to be provided exactly as (A). They only
   need to be sufficient to ensure that for their argument num of integer type,
   std::fabs(num) has the same effect as std::fabs(static_cast<double>(num)).

Example
// Run this code
 #include <cmath>
 #include <iostream>
 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'
               << "abs(-NaN) = " << std::abs(-NAN) << '\n';
 }

Possible output:
 abs(+3.0) = 3
 abs(-3.0) = 3
 abs(-0.0) = 0
 abs(-Inf) = inf
 abs(-NaN) = nan
   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
                       overloads of std::abs for integer types
   LWG 2735 C++11 returning double was erroneously removed the requirement
                       required

See also
   abs(int)
   labs computes absolute value of an integral value (\(\small{|x|}\)|x|)
   llabs (function)
   (C++11)
   copysign
   copysignf
   copysignl copies the sign of a floating point value
   (C++11) (function)
   (C++11)
   (C++11)
   signbit checks if the given number is negative
   (C++11) (function)
   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
   fabs