NAME¶

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)
(constexpr since C++23)
float fdimf( float x, float y ); (2) (since C++11)
(constexpr since C++23)
double fdim ( double x, double y ); (3) (since C++11)
(constexpr since C++23)
long double fdim ( long double x, long double y ); (4) (since C++11)
(constexpr since C++23)
long double fdiml( long double x, long double y ); (5) (since C++11)
(constexpr since C++23)
Promoted fdim ( Arithmetic1 x, Arithmetic2 y ); (6) (since C++11)
(constexpr since C++23)

1-5) Returns the positive difference between x and y, that is, if x>y, returns x-y,
otherwise (if x≤y), returns +0.
6) A set of overloads or a function template for all combinations of arguments of
arithmetic type not covered by (1-5). 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>
#ifndef __GNUC__
#pragma STDC FENV_ACCESS ON
#endif
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

See also¶

abs(int)
labs computes absolute value of an integral value (\(\small{|x|}\)|x|)
llabs (function)
(C++11)
fmax
fmaxf
fmaxl larger of two floating-point values
(C++11) (function)
(C++11)
(C++11)