| Defined in header <math.h> | ||||
|---|---|---|---|---|
| (1) | (since C99) | ||
| (2) | (since C99) | ||
| (3) | (since C99) | ||
| Defined in header <tgmath.h> | ||||
| (7) | (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.Parameters
| x, y | - | floating point values |
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.
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_INEXACTis never raised) and independent of the current rounding mode.
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).
Example
1 2 3 4 5 6 7 8 9 10 | #include <stdio.h>#include <math.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:
1 2 3 4 | copysign(1.0,+2.0) = +1.0copysign(1.0,-2.0) = -1.0copysign(INFINITY,-2.0) = -infcopysign(NAN,-2.0) = -nan |
References
- 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)
See also
| (C99)(C99) | computes absolute value of a floating-point value (|x|) (function) |
| (C99) | checks if the given number is negative (function) |
C++ documentation for copysign | |
Please login to continue.