Common mathematical functions| Functions | | Basic operations | | | | Maximum/minimum operations | | | | Exponential functions | | | | Power functions | | | | Trigonometric and hyperbolic functions | | |
| | Nearest integer floating-point | | | | Floating-point manipulation | | | | Narrowing operations | | | | Quantum and quantum exponent | | | | Decimal re-encoding functions | | | | Total order and payload functions | | | | Classification | | |
| | Error and gamma functions | | | | Types | | | | Macro constants | | Special floating-point values | | | | Arguments and return values | | (C99)(C99)(C99)(C99)(C99) |
| | (C23)(C23)(C23)(C23)(C23) |
| | Error handling | | | | Fast operation indicators | | |
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float copysignf(float x,float y); | (1) | (since C99) |
double copysign(double x,double y); | (2) | (since C99) |
longdouble copysignl(longdouble x,longdouble y); | (3) | (since C99) |
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#define copysign(x, y) | (4) | (since C99) |
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1-3) Composes a floating-point value with the magnitude ofx and the sign ofy.
4) Type-generic macro: If any argument has typelongdouble,copysignl is called. Otherwise, if any argument has integer type or has typedouble,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 ofx and the sign ofy is returned.
Ifx is NaN, then NaN with the sign ofy is returned.
Ify 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 inmath_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
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
#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) = +1.0copysign(1.0,-2.0) = -1.0copysign(INFINITY,-2.0) = -infcopysign(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
| computes absolute value of a floating-point value (\(\small{|x|}\)|x|)
(function)[edit] |
| checks if the given number is negative
(function macro)[edit] |
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