NAME

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

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #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 feature_test_macros(7)):

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

       rint():
           _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

       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 argument.

RETURN VALUE

       These functions return the rounded integer value.

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

ERRORS

       No errors occur.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ nearbyint(), nearbyintf(), nearbyintl(), rint(), rintf(), rintl()           │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C99, POSIX.1-2001.

       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 was 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, 53).)  This was removed in POSIX.1-2008.

       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) instead.

SEE ALSO

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

Linux man-pages 6.9.1                              2024-06-16                                            rint(3)