Originální popis anglicky:
fdim, fdimf, fdiml - compute positive difference between two floating-point
numbers
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double fdim(double
x, double
y);
float fdimf(float
x, float
y);
long double fdiml(long double
x, long double
y);
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.
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), or 0.0 (if
supported), or an implementation-defined value shall be returned.
If
x or
y is 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
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:
- Range Error
- The result underflows.
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.
None.
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.
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
.
