IEEE Std 1003.1-2001

Copyright © 2001 The IEEE and The Open Group, All Rights reserved.

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 IEEE Std 1003.1-2001 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

x-yis positive and underflows, a range error may occur, and either (x-y) (if representable),^{[XSI]}or 0.0 (if supported), or an implementation-defined value shall be returned.

^{[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, then

errnoshall 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, then

errnoshall 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 implementations supporting IEEE Std 754-1985,

x-ycannot underflow, and hence the 0.0 return value is shaded as an extension for implementations supporting the XSI extension rather than an MX extension.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() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>

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

POSIX ® is a registered Trademark of The IEEE.

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