PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       nextafter, nextafterf, nextafterl, nexttoward, nexttowardf,
       nexttowardl — next representable floating-point number

SYNOPSIS         top

       #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         top

       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         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       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         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       feclearexcept(3p), fetestexcept(3p)

       The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment
       of Error Conditions for Mathematical Functions, math.h(0p),
       tgmath.h(0p)

COPYRIGHT         top

       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 .

IEEE/The Open Group                 2013                       NEXTAFTER(3P)

Pages that refer to this page: math.h(0p)