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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  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 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
       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>
COPYRIGHT
       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 Electri-
       cal  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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                        NEXTAFTER(3P)