# nextafterf

```NEXTAFTER(3)               Linux Programmer's Manual              NEXTAFTER(3)

NAME
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl
- floating-point number manipulation

SYNOPSIS
#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);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

nextafter():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
nextafterf(), nextafterl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
nexttoward(), nexttowardf(), nexttowardl():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99

DESCRIPTION
The nextafter(), nextafterf(), and nextafterl()  functions  return  the
next representable floating-point value following x in the direction of
y.  If y is less than x, these functions will return the largest repre-
sentable number less than x.

If x equals y, the functions return y.

The  nexttoward(),  nexttowardf(),  and  nexttowardl() functions do the
same as the corresponding nextafter() functions, except that they  have
a long double second argument.

RETURN VALUE
On  success,  these  functions  return the next representable floating-
point value after x in the direction of y.

If x equals y, then y (cast to the same type as x) is returned.

If x or y is a NaN, a NaN is returned.

If x is finite, and the result would overflow, a  range  error  occurs,
and  the  functions  return  HUGE_VAL, HUGE_VALF, or HUGE_VALL, respec-
tively, with the correct mathematical sign.

If x is not equal to y, and the correct function result would  be  sub-
normal,  zero,  or underflow, a range error occurs, and either the cor-
rect value (if it can be represented), or 0.0, is returned.

ERRORS
See math_error(7) for information on how to determine whether an  error
has occurred when calling these functions.

The following errors can occur:

Range error: result overflow
An overflow floating-point exception (FE_OVERFLOW) is raised.

Range error: result is subnormal or underflows
An underflow floating-point exception (FE_UNDERFLOW) is raised.

These functions do not set errno.

ATTRIBUTES
For   an   explanation   of   the  terms  used  in  this  section,  see
attributes(7).

+-----------------------------+---------------+---------+
|Interface                    | Attribute     | Value   |
+-----------------------------+---------------+---------+
|nextafter(), nextafterf(),   | Thread safety | MT-Safe |
|nextafterl(), nexttoward(),  |               |         |
|nexttowardf(), nexttowardl() |               |         |
+-----------------------------+---------------+---------+
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.  This function is defined in  IEC  559
(and the appendix with recommended functions in IEEE 754/IEEE 854).

BUGS
In  glibc  version  2.5  and  earlier,  these functions do not raise an
underflow floating-point (FE_UNDERFLOW)  exception  when  an  underflow
occurs.