NEXTAFTER(3) Linux Programmer's Manual NEXTAFTER(3)
nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl - floating-point
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);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
nextafter(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or
nextafterf(), nextafterl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE; or cc -std=c99
nexttoward(), nexttowardf(), nexttowardl(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE;
The nextafter() 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 rep-
resentable number less than x.
If x equals y, the functions return y.
The nexttoward() functions do the same as the nextafter() functions, except that they have
a long double second argument.
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, respectively, with the correct mathematical
If x is not equal to y, and the correct function result would be subnormal, zero, or
underflow, a range error occurs, and either the correct value (if it can be represented),
or 0.0, is returned.
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.
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended
functions in IEEE 754/IEEE 854).
In glibc version 2.5 and earlier, these functions do not raise an underflow floating-point
(FE_UNDERFLOW) exception when an underflow occurs.
This page is part of release 3.25 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at http://www.ker-
GNU 2009-12-05 NEXTAFTER(3)