nextafter(3) — Linux manual page

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

NAME         top

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

SYNOPSIS         top

```       #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():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

nextafterf(), nextafterl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

nexttoward(), nexttowardf(), nexttowardl():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
|| _POSIX_C_SOURCE >= 200112L
```

DESCRIPTION         top

```       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 representable 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         top

```       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 sign.

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.
```

ERRORS         top

```       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
errno is set to ERANGE.  An overflow floating-point
exception (FE_OVERFLOW) is raised.

Range error: result is subnormal or underflows
errno is set to ERANGE.  An underflow floating-point
exception (FE_UNDERFLOW) is raised.
```

ATTRIBUTES         top

```       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         top

```       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         top

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

Before glibc version 2.23 these functions did not set errno.
```

```       nearbyint(3)
```

COLOPHON         top

```       This page is part of release 5.13 of the Linux man-pages project.
A description of the project, information about reporting bugs,