nextup(3) — Linux manual page

nextup(3)                Library Functions Manual               nextup(3)

NAME         top

       nextup, nextupf, nextupl, nextdown, nextdownf, nextdownl - return
       next floating-point number toward positive/negative infinity

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #define _GNU_SOURCE     /* See feature_test_macros(7) */
       #include <math.h>

       double nextup(double x);
       float nextupf(float x);
       long double nextupl(long double x);

       double nextdown(double x);
       float nextdownf(float x);
       long double nextdownl(long double x);

DESCRIPTION         top

       The nextup(), nextupf(), and nextupl() functions return the next
       representable floating-point number greater than x.

       If x is the smallest representable negative number in the
       corresponding type, these functions return -0.  If x is +0 or -0,
       the returned value is the smallest representable positive number
       of the corresponding type.

       If x is positive infinity, the returned value is positive
       infinity.  If x is negative infinity, the returned value is the
       largest representable finite negative number of the corresponding
       type.

       If x is NaN, the returned value is NaN.

       The value returned by nextdown(x) is -nextup(-x), and similarly
       for the other types.

RETURN VALUE         top

       See DESCRIPTION.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                            │ Attribute     │ Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │ nextup(), nextupf(), nextupl(),      │ Thread safety │ MT-Safe │
       │ nextdown(), nextdownf(), nextdownl() │               │         │
       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS         top

       These functions are described in IEEE Std 754-2008 - Standard for
       Floating-Point Arithmetic and ISO/IEC TS 18661.

HISTORY         top

       glibc 2.24.

SEE ALSO         top

       nearbyint(3), nextafter(3)

COLOPHON         top

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Linux man-pages 6.15            2025-05-17                      nextup(3)

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