nextafter(3) - Linux manual page (original) (raw)

nextafter(3) Library Functions Manual nextafter(3)

NAME top

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

LIBRARY top

   Math library (_libm_, _-lm_)

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)](../man7/math%5Ferror.7.html) 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](../man3/errno.3.html)_ is set to **ERANGE**.  An overflow floating-point
          exception (**FE_OVERFLOW**) is raised.

   Range error: result is subnormal or underflows
          _[errno](../man3/errno.3.html)_ 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)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **nextafter**(), **nextafterf**(),           │ Thread safety │ MT-Safe │
   │ **nextafterl**(), **nexttoward**(),          │               │         │
   │ **nexttowardf**(), **nexttowardl**()         │               │         │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   C11, POSIX.1-2008.

   This function is defined in IEC 559 (and the appendix with
   recommended functions in IEEE 754/IEEE 854).

HISTORY top

   C99, POSIX.1-2001.

BUGS top

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

   Before glibc 2.23 these functions did not set _[errno](../man3/errno.3.html)_.

SEE ALSO top

   [nearbyint(3)](../man3/nearbyint.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 nextafter(3)

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