nextafter(3p) — Linux manual page

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.1‐2017 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.1‐2017, Section 4.20,
       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 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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               2017                     NEXTAFTER(3P)

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