NAME

       nextafter,  nextafterf,  nextafterl,  nexttoward, nexttowardf, nexttowardl - next representable floating-
       point number

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);

DESCRIPTION

       The nextafter(), nextafterf(), and nextafterl() functions shall compute the next representable  floating-
       point  value  following x in the direction of y.  Thus, if y is less than x, nextafter() shall return the
       largest representable floating-point number less than x. The nextafter(), nextafterf(), and  nextafterl()
       functions shall return y if x equals y.

       The  nexttoward(),  nexttowardf(),  and  nexttowardl() functions shall be equivalent to the corresponding
       nextafter() functions, except that the second parameter shall have type long  double  and  the  functions
       shall return y converted to the type of the function if x equals y.

       An   application   wishing   to   check   for  error  situations  should  set  errno  to  zero  and  call
       feclearexcept(FE_ALL_EXCEPT) before calling  these  functions.   On  return,  if  errno  is  non-zero  or
       fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

RETURN VALUE

       Upon  successful  completion,  these  functions  shall return the next representable floating-point value
       following x in the direction of y.

       If x== y, y (of the type x) shall be returned.

       If x is finite and the correct function value would overflow, a range error shall  occur  and  ±HUGE_VAL,
       ±HUGE_VALF, and ±HUGE_VALL (with the same sign as x) shall be returned as appropriate for the return type
       of the function.

       If x or y is NaN, a NaN shall be returned.

       If x!= y and the correct function value is subnormal, zero, or underflows, a range error shall occur, and
       either the correct function value (if representable) or 0.0 shall be returned.

ERRORS

       These functions shall fail if:

       Range Error
              The correct value overflows.

       If  the  integer  expression  (math_errhandling  &  MATH_ERRNO)  is  non-zero, then errno shall be set to
       [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,  then  the  overflow
       floating-point exception shall be raised.

       Range Error
              The correct value is subnormal or underflows.

       If  the  integer  expression  (math_errhandling  &  MATH_ERRNO)  is  non-zero, then errno shall be set to
       [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then  the  underflow
       floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       On  error,  the  expressions  (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are
       independent of each other, but at least one of them must be non-zero.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       feclearexcept() , fetestexcept() , the Base Definitions volume  of  IEEE Std 1003.1-2001,  Section  4.18,
       Treatment of Error Conditions for Mathematical Functions, <math.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc and The Open Group. In the event of any discrepancy between this version and the  original  IEEE  and
       The  Open  Group  Standard,  the  original  IEEE and The Open Group Standard is the referee document. The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                          NEXTAFTER(P)