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

**#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():

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

nextafterf(), nextafterl():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

nexttoward(), nexttowardf(), nexttowardl():

_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

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.

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.

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`

.

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

Interface | Attribute | Value |

nextafter(), nextafterf(), nextafterl(), nexttoward(), nexttowardf(), nexttowardl() |
Thread safety | MT-Safe |

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).

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

nearbyint(3)

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