Std::fdim,std::fdimf,std::fdiml (3) Linux Manual Page

std::fdim,std::fdimf,std::fdiml – std::fdim,std::fdimf,std::fdiml

Synopsis

Defined in header <cmath>
float fdim ( float x, float y ); (1) (since C++11)
float fdimf( float x, float y );
double fdim ( double x, double y ); (2) (since C++11)
long double fdim ( long double x, long double y ); (3) (since C++11)
long double fdiml( long double x, long double y );
Promoted fdim ( Arithmetic1 x, Arithmetic2 y ); (4) (since C++11)
1-3) Returns the positive difference between x and y, that is, if x>y, returns x-y, otherwise (if x≤y), returns +0.
4) A set of overloads or a function template for all combinations of arguments of arithmetic_type not covered by 1-3). If any argument has integral_type, it is cast to double. If any argument is long double, then the return type Promoted is also long double, otherwise the return type is always double.

Parameters

x, y – values of floating-point or integral_types

Return value

If successful, returns the positive difference between x and y.
If a range error due to overflow occurs, +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL is returned.
If a range error due to underflow occurs, the correct value (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),

* If either argument is NaN, NaN is returned

Notes

Equivalent to std::fmax(x-y, 0), except for the NaN handling requirements.

Example

// Run this code

#include <iostream>

#include <cmath>

#include <cerrno>

#include <cstring>

#include <cfenv>

#pragma STDC FENV_ACCESS ON

int main()

{
    std::cout << "fdim(4, 1) = " << std::fdim(4, 1)
              << " fdim(1, 4) = " << std::fdim(1, 4) << '\n'
              << "fdim(4,-1) = " << std::fdim(4, -1)
              << " fdim(1,-4) = " << std::fdim(1, -4) << '\n';
    // error handling
    errno = 0;
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "fdim(1e308, -1e308) = " << std::fdim(1e308, -1e308) << '\n';
    if (errno == ERANGE)
        std::cout << "    errno == ERANGE: " << std::strerror(errno) << '\n';
    if (std::fetestexcept(FE_OVERFLOW))
        std::cout << "    FE_OVERFLOW raised\n";
}

Output:

  fdim(4, 1) = 3 fdim(1, 4) = 0
  fdim(4,-1) = 5 fdim(1,-4) = 5
  fdim(1e308, -1e308) = inf
      errno == ERANGE: Numerical result out of range
      FE_OVERFLOW raised

std::fdim,std::fdimf,std::fdiml (3) Linux Manual Page