fdim (3p) - Linux Manuals
fdim: compute positive difference between two floating-point
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.NAME
fdim, fdimf, fdiml - compute positive difference between two floating-point numbers
SYNOPSIS
#include <math.h>
double fdim(double x, double y);
float fdimf(float x, float y);
long double fdiml(long double x, long double y);
DESCRIPTION
These functions shall determine the positive difference between their arguments. If x is greater than y, x- y is returned. If x is less than or equal to y, +0 is returned.
An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.
RETURN VALUE
Upon successful completion, these functions shall return the positive difference value.
If x- y is positive and overflows, a range error shall occur and fdim(), fdimf(), and fdiml() shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If x- y is positive and underflows, a range error may
occur, and either ( x- y) (if representable),
If
x or y is NaN, a NaN shall be returned.
The fdim() function shall fail if:
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall 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:
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall 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.
On implementations supporting IEEE Std 754-1985, x- y
cannot 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.
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>
ERRORS
EXAMPLES
APPLICATION USAGE
RATIONALE
FUTURE DIRECTIONS
COPYRIGHT
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 .
SEE ALSO