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.  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(),      │ Thread safety │ MT-Safe │
       │rintl()                                                        │               │         │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C99, POSIX.1-2001.

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  127  (respectively,  1023),  and the number of mantissa bits
       including the implicit bit 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)