bionic (3) nextafter.3posix.gz

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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 functionality described on this reference page is aligned  with  the  ISO C  standard.  Any  conflict
       between  the  requirements  described  here  and  the  ISO C  standard  is  unintentional. This volume of
       POSIX.1‐2008 defers to the ISO C standard.

       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
       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.

       When  <tgmath.h>  is  included,  note  that  the return type of nextafter() depends on the generic typing
       deduced from both arguments, while the return type of nexttoward() depends only on the generic typing  of
       the first argument.


RATIONALE
       None.


FUTURE DIRECTIONS
       None.


SEE ALSO
       feclearexcept(), fetestexcept()

       The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of Error Conditions for Mathematical
       Functions, <math.h>, <tgmath.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers,  Inc
       and  The  Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .