### 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***);**

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
*cc -std=c99* **nextafterf**(), **nextafterl**(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
*cc -std=c99* **nexttoward**(), **nexttowardf**(), **nexttowardl**(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE;
*cc -std=c99*

### DESCRIPTION

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 representable number less than
*y*.

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.

### 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**, 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

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.
| |

*errno*.

### CONFORMING TO

C99, POSIX.1-2001. 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.

### SEE ALSO

### COLOPHON

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A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.