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Difference between revisions of "cpp/numeric/math/fdim"

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< cpp‎ | numeric‎ | math
m (link integral type)
m (.)
 
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{{cpp/title|fdim}}
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{{cpp/title|fdim|fdimf|fdiml}}
 
{{cpp/numeric/math/navbar}}
 
{{cpp/numeric/math/navbar}}
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{{dcl begin}}
+
{{cpp/numeric/math/declarations
−
{{dcl header | cmath}}
+
|family=fdim
−
{{dcl | since=c++11 | num=1 |
+
|param1=x
−
float      fdim( float x, float y );
+
|param2=y
 +
|constexpr_since=23
 +
|desc=Returns the positive difference between {{c|x}} and {{c|y}}, that is, if {{c|x > y}}, returns {{c|x - y}}, otherwise (i.e. if {{c|1=x <= y}}) returns {{c|+0}}.
 
}}
 
}}
−
{{dcl | since=c++11 | num=2 |
 
−
double      fdim( double x, double y );
 
−
}}
 
−
{{dcl | since=c++11 | num=3 |
 
−
long double fdim( long double x, long double y );
 
−
}}
 
−
{{dcl | since=c++11 | num=4 |
 
−
Promoted    fdim( Arithmetic1 x, Arithmetic2 y );
 
−
}}
 
−
{{dcl end}}
 
−
 
−
Returns the positive difference between {{c|x}} and {{c|y}}.
 
−
This could be implemented as {{c|fmax (x - y, 0)}}, so if {{c|x ≤ y}}, the result is always equals to 0, otherwise it is {{c|x - y}}.
 
−
 
−
4) If any argument has [[cpp/types/is_integral|integral type]], it is cast to {{c|double}}. If any other argument is {{c|long double}}, then the return type is {{c|long double}}, otherwise it is {{c|double}}.
 
  
 
===Parameters===
 
===Parameters===
 
{{par begin}}
 
{{par begin}}
−
{{par | x, y | values of floating-point or [[cpp/types/is_integral|integral types]]}}
+
{{par|x, y|floating-point or integer values}}
 
{{par end}}
 
{{par end}}
  
 
===Return value===
 
===Return value===
−
The positive difference value.
+
If successful, returns the positive difference between {{c|x}} and {{c|y}}.
 +
 
 +
If a range error due to overflow occurs, {{lc|HUGE_VAL|+HUGE_VAL}}, {{tt|+HUGE_VALF}}, or {{tt|+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 {{lc|math_errhandling}}.
 +
 
 +
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
 +
* If either argument is NaN, NaN is returned.
 +
 
 +
===Notes===
 +
Equivalent to {{c|std::fmax(x - y, 0)}}, except for the NaN handling requirements.
 +
 
 +
{{cpp/numeric/math/additional overload note|fdim}}
 +
 
 +
===Example===
 +
{{example
 +
|code=
 +
#include <cerrno>
 +
#include <cfenv>
 +
#include <cmath>
 +
#include <cstring>
 +
#include <iostream>
 +
 
 +
#ifndef __GNUC__
 +
#pragma STDC FENV_ACCESS ON
 +
#endif
 +
 
 +
int main()
 +
{
 +
    std::cout << "fdim(4, 1) = " << std::fdim(4, 1) << '\n'
 +
              << "fdim(1, 4) = " << std::fdim(1, 4) << '\n'
 +
              << "fdim(4,-1) = " << std::fdim(4, -1) << '\n'
 +
              << "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===
 
===See also===
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc inc | cpp/numeric/math/dsc abs}}
+
{{dsc inc|cpp/numeric/math/dsc abs}}
−
{{dsc inc | cpp/numeric/math/dsc fmax}}
+
{{dsc inc|cpp/numeric/math/dsc fmax}}
−
{{dsc see c | c/numeric/math/fdim}}
+
{{dsc see c|c/numeric/math/fdim}}
 
{{dsc end}}
 
{{dsc end}}
  
−
[[de:cpp/numeric/math/fdim]]
+
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
−
[[es:cpp/numeric/math/fdim]]
+
−
[[fr:cpp/numeric/math/fdim]]
+
−
[[it:cpp/numeric/math/fdim]]
+
−
[[ja:cpp/numeric/math/fdim]]
+
−
[[pt:cpp/numeric/math/fdim]]
+
−
[[ru:cpp/numeric/math/fdim]]
+
−
[[zh:cpp/numeric/math/fdim]]
+

Latest revision as of 09:22, 15 October 2023

 
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Common mathematical functions
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fdim
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Defined in header <cmath>
(1)
float       fdim ( float x, float y );

double      fdim ( double x, double y );

long double fdim ( long double x, long double y );
 (until C++23)
constexpr /* floating-point-type */

            fdim ( /* floating-point-type */ x,

                   /* floating-point-type */ y );
 (since C++23)
float       fdimf( float x, float y );
 (2) (since C++11)
(constexpr since C++23)
long double fdiml( long double x, long double y );
 (3) (since C++11)
(constexpr since C++23)
Additional overloads (since C++11)
Defined in header <cmath>
template< class Integer >
double      fdim ( Integer x, Integer y );
 (A) (constexpr since C++23)
1-3) Returns the positive difference between x and y, that is, if x > y, returns x - y, otherwise (i.e. if x <= y) returns +0. The library provides overloads of std::fdim for all cv-unqualified floating-point types as the type of the parameters.(since C++23)
A) Additional overloads are provided for all integer types, which are treated as double.
 (since C++11)

Contents

[edit] Parameters

x, y - floating-point or integer values

[edit] 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.

[edit] 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.

[edit] Notes

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

The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their first argument num1 and second argument num2:

  • If num1 or num2 has type long double, then std::fdim(num1, num2) has the same effect as std::fdim(static_cast<long double>(num1),
              static_cast<long double>(num2))    .
  • Otherwise, if num1 and/or num2 has type double or an integer type, then std::fdim(num1, num2) has the same effect as std::fdim(static_cast<double>(num1),
              static_cast<double>(num2))    .
  • Otherwise, if num1 or num2 has type float, then std::fdim(num1, num2) has the same effect as std::fdim(static_cast<float>(num1),
              static_cast<float>(num2))    .
(until C++23)

If num1 and num2 have arithmetic types, then std::fdim(num1, num2) has the same effect as std::fdim(static_cast</* common-floating-point-type */>(num1),
          static_cast</* common-floating-point-type */>(num2)), where /* common-floating-point-type */ is the floating-point type with the greatest floating-point conversion rank and greatest floating-point conversion subrank between the types of num1 and num2, arguments of integer type are considered to have the same floating-point conversion rank as double.

If no such floating-point type with the greatest rank and subrank exists, then overload resolution does not result in a usable candidate from the overloads provided.

(since C++23)

[edit] Example

Run this code
#include <cerrno>
#include <cfenv>
#include <cmath>
#include <cstring>
#include <iostream>
 
#ifndef __GNUC__
#pragma STDC FENV_ACCESS ON
#endif
 
int main()
{
    std::cout << "fdim(4, 1) = " << std::fdim(4, 1) << '\n'
              << "fdim(1, 4) = " << std::fdim(1, 4) << '\n'
              << "fdim(4,-1) = " << std::fdim(4, -1) << '\n'
              << "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

[edit] See also

(C++11)
 computes absolute value of an integral value (|x|)
(function) [edit]
(C++11)(C++11)(C++11)
 larger of two floating-point values
(function) [edit]
C documentation for fdim
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