Manpages - nextafter.3

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 <= 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

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

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.

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

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.

Before glibc version 2.23 these functions did not set errno.

*nearbyint*(3)

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