copysign, copysignf, copysignl
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Defined in header
<math.h>
float copysignf( float x, float y );
(1)
(since C99)
double copysign( double x, double y );
(2)
(since C99)
long double copysignl( long double x, long double y );
(3)
(since C99)
Defined in header
<tgmath.h>
#define copysign(x, y)
(4)
(since C99)
1-3) Composes a floating-point value with the magnitude of
x and the sign of y.4) Type-generic macro: If any argument has type long double,
copysignl is called. Otherwise, if any argument has integer type or has type double, copysign is called. Otherwise, copysignf is called.[edit] Parameters
x, y
-
floating-point values
[edit] Return value
If no errors occur, the floating-point value with the magnitude of x and the sign of y is returned.
If x is NaN, then NaN with the sign of y is returned.
If y is -0, the result is only negative if the implementation supports the signed zero consistently in arithmetic operations.
[edit] Error handling
This function is not subject to any errors specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- The returned value is exact (FE_INEXACT is never raised) and independent of the current rounding mode.
[edit] Notes
copysign is the only portable way to manipulate the sign of a NaN value (to examine the sign of a NaN, signbit may also be used).
[edit] Example
Run this code
#include <math.h> #include <stdio.h> int main(void) { printf ("copysign(1.0,+2.0) = %+.1f\n", copysign(1.0,+2.0)); printf ("copysign(1.0,-2.0) = %+.1f\n", copysign(1.0,-2.0)); printf ("copysign(INFINITY,-2.0) = %f\n", copysign(INFINITY,-2.0)); printf ("copysign(NAN,-2.0) = %f\n", copysign(NAN,-2.0)); }
Possible output:
copysign(1.0,+2.0) = +1.0 copysign(1.0,-2.0) = -1.0 copysign(INFINITY,-2.0) = -inf copysign(NAN,-2.0) = -nan
[edit] References
- C23 standard (ISO/IEC 9899:2024):
- 7.12.11.1 The copysign functions (p: TBD)
- 7.25 Type-generic math <tgmath.h> (p: TBD)
- F.10.8.1 The copysign functions (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.12.11.1 The copysign functions (p: TBD)
- 7.25 Type-generic math <tgmath.h> (p: TBD)
- F.10.8.1 The copysign functions (p: TBD)
- C11 standard (ISO/IEC 9899:2011):
- 7.12.11.1 The copysign functions (p: 255)
- 7.25 Type-generic math <tgmath.h> (p: 373-375)
- F.10.8.1 The copysign functions (p: 529)
- C99 standard (ISO/IEC 9899:1999):
- 7.12.11.1 The copysign functions (p: 236)
- 7.22 Type-generic math <tgmath.h> (p: 335-337)
- F.9.8.1 The copysign functions (p: 465)
[edit] See also
C++ documentation for copysign