IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)

Copyright © 2001-2018 IEEE and The Open Group

fdim, fdimf, fdiml - compute positive difference between two floating-point numbers

#include <math.h>

double fdim(doublex, doubley);

float fdimf(floatx, floaty);

long double fdiml(long doublex, long doubley);

^{[CX]}The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.These functions shall determine the positive difference between their arguments. If

xis greater thany,x-yis returned. Ifxis less than or equal toy, +0 is returned.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Upon successful completion, these functions shall return the positive difference value.

If

x-yis positive and overflows, a range error shall occur andfdim(),fdimf(), andfdiml() shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.If the correct value would cause underflow, a range error may occur, and

fdim(),fdimf(), andfdiml() shall return^{[MXX]}the correct value, or (if the IEC 60559 Floating-Point option is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

^{[MX]}Ifxoryis NaN, a NaN shall be returned.

The

fdim() function shall fail if:

- Range Error
- The result overflows.
If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.The

fdim() function may fail if:

- Range Error
- The result underflows.
If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling& MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

None.

On error, the expressions (

math_errhandling& MATH_ERRNO) and (math_errhandling& MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

None.

None.

feclearexcept,fetestexcept,fmax,fmin

Treatment of Error Conditions for Mathematical Functions,<math.h>

First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0119 [68,428] and XSH/TC1-2008/0120 [68,428] are applied.

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