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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 .