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COPYSIGN(3) Library Functions Manual COPYSIGN(3) NAME copysign, copysignf, copysignl - functions to manipulate signs LIBRARY Math Library (libm, -lm) SYNOPSIS #include <math.h> double copysign(double x, double y); float copysignf(float x, float y); long double copysignl(long double x, long double y); DESCRIPTION The copysign(), copysignf(), and copysignl() functions return a value whose absolute value matches x, but whose sign bit is taken from y. RETURN VALUES Upon successful completion, all three functions return a value with the magnitude of x and the sign of y. If x is NaN , the functions return a NaN with the sign of y. SEE ALSO math(3), signbit(3) STANDARDS The described functions conform to ISO/IEC 9899:1999 ("ISO C99"). CAVEATS Note that on implementations that represent a signed zero but do not treat negative zero consistently in arithmetic operations, these functions may regard the sign of zero as positive. NetBSD 8.0 April 13, 2011 NetBSD 8.0