Originální popis anglicky:
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - next
representable floating-point number
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double nextafter(double
x, double
y);
float nextafterf(float
x, float
y );
long double nextafterl(long double
x, long
double y);
double nexttoward(double
x, long double
y );
float nexttowardf(float
x, long double
y );
long double nexttowardl(long double
x, long
double y);
The
nextafter(),
nextafterf(), and
nextafterl() functions
shall compute the next representable floating-point value following
x
in the direction of
y. Thus, if
y is less than
x,
nextafter() shall return the largest representable floating-point
number less than
x. The
nextafter(),
nextafterf(), and
nextafterl() functions shall return
y if
x equals
y.
The
nexttoward(),
nexttowardf(), and
nexttowardl()
functions shall be equivalent to the corresponding
nextafter()
functions, except that the second parameter shall have type
long double
and the functions shall return
y converted to the type of the function
if
x equals
y.
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 next representable
floating-point value following
x in the direction of
y.
If
x==
y,
y (of the type
x) shall be returned.
If
x is finite and the correct function value would overflow, a range
error shall occur and ±HUGE_VAL, ±HUGE_VALF, and
±HUGE_VALL (with the same sign as
x) shall be returned as
appropriate for the return type of the function.
If
x or
y is NaN, a NaN shall be returned.
If
x!=
y and the correct function value is subnormal, zero, or
underflows, a range error shall occur, and either the correct function value
(if representable) or 0.0 shall be returned.
These functions shall fail if:
- Range Error
- The correct value 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.
- Range Error
- The correct value is subnormal or 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 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() , 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
.
