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 .