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RINT(3)                                                                 Linux Programmer's Manual                                                                RINT(3)

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

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);

       Link with -lm.

   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.  POSIX.1-2001 documents a range error for overflows, but see NOTES.

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 │
       └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

NOTES
       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  128  (respec‐
       tively, 1024), and the number of mantissa bits is 24 (respectively, 53).)

       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)

                                                                               2021-03-22                                                                        RINT(3)