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NEXTAFTER(P)			    POSIX Programmer's Manual			     NEXTAFTER(P)

NAME
       nextafter,  nextafterf,	nextafterl,  nexttoward,  nexttowardf,	nexttowardl - next repre-
       sentable 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  repre-
       sentable  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				     NEXTAFTER(P)
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