huschi.net

NEXTAFTER(3P)              POSIX Programmer's Manual             NEXTAFTER(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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  direc-
       tion  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 rep-
       resentable 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 under-
       flows, 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(3P)