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

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< cpp‎ | numeric‎ | math
 
 
 
Common mathematical functions
Functions
Basic operations
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
fdim
(C++11)
(C++11)(C++11)(C++11)
Exponential functions
(C++11)
(C++11)
(C++11)
(C++11)
Power functions
(C++11)
(C++11)
Trigonometric and hyperbolic functions
(C++11)
(C++11)
(C++11)
Error and gamma functions
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(C++11)
Nearest integer floating point operations
(C++11)(C++11)(C++11)
(C++11)
(C++11)
(C++11)(C++11)(C++11)
Floating point manipulation functions
(C++11)(C++11)
(C++11)
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(C++11)(C++11)
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Classification/Comparison
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Macro constants
(C++11)(C++11)(C++11)(C++11)(C++11)
 
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

#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

computes absolute value of an integral value (|x|)
(function)
(C++11)(C++11)(C++11)
larger of two floating-point values
(function)