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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);

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), or 0.0 (if supported), or an implementation-defined value shall be returned.If

xoryis NaN, a NaN shall be returned.

The

fdim() function shall fail if:If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

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. 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.

The following sections are informative.

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>

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group |
FDIM (P) | 2003 |