rint(3) — Linux manual page


rint(3)                 Library Functions Manual                 rint(3)

NAME         top

       nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl - round to
       nearest integer

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #include <math.h>

       double nearbyint(double x);
       float nearbyintf(float x);
       long double nearbyintl(long double x);

       double rint(double x);
       float rintf(float x);
       long double rintl(long double x);

   Feature Test Macro Requirements for glibc (see

       nearbyint(), nearbyintf(), nearbyintl():
           _POSIX_C_SOURCE >= 200112L || _ISOC99_SOURCE

           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       rintf(), rintl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       The nearbyint(), nearbyintf(), and nearbyintl() functions round
       their argument to an integer value in floating-point format,
       using the current rounding direction (see fesetround(3)) and
       without raising the inexact exception.  When the current rounding
       direction is to nearest, these functions round halfway cases to
       the even integer in accordance with IEEE-754.

       The rint(), rintf(), and rintl() functions do the same, but will
       raise the inexact exception (FE_INEXACT, checkable via
       fetestexcept(3)) when the result differs in value from the

RETURN VALUE         top

       These functions return the rounded integer value.

       If x is integral, +0, -0, NaN, or infinite, x itself is returned.

ERRORS         top

       No errors occur.  POSIX.1-2001 documents a range error for
       overflows, but see NOTES.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ nearbyint(), nearbyintf(),          │ Thread safety │ MT-Safe │
       │ nearbyintl(), rint(), rintf(),      │               │         │
       │ rintl()                             │               │         │

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       C99, POSIX.1-2001.

NOTES         top

       SUSv2 and POSIX.1-2001 contain text about overflow (which might
       set errno to ERANGE, or raise an FE_OVERFLOW exception).  In
       practice, the result cannot overflow on any current machine, so
       this error-handling stuff is just nonsense.  (More precisely,
       overflow can happen only when the maximum value of the exponent
       is smaller than the number of mantissa bits.  For the IEEE-754
       standard 32-bit and 64-bit floating-point numbers the maximum
       value of the exponent is 127 (respectively, 1023), and the number
       of mantissa bits including the implicit bit is 24 (respectively,

       If you want to store the rounded value in an integer type, you
       probably want to use one of the functions described in lrint(3)

SEE ALSO         top

       ceil(3), floor(3), lrint(3), round(3), trunc(3)

Linux man-pages (unreleased)     (date)                          rint(3)

Pages that refer to this page: abs(3)ceil(3)fabs(3)floor(3)lrint(3)lround(3)nextafter(3)nextup(3)round(3)roundup(3)trunc(3)