Section (3) rint
nearbyint, nearbyintf, nearbyintl, rint, rintf, rintl — round to nearest integer
||long double x
||long double x
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.
rintl() functions do the same, but will
raise the inexact
checkable via fetestexcept(3)) when the
result differs in value from the argument.
These functions return the rounded integer value.
x is integral,
+0, −0, NaN, or infinite,
x itself is returned.
For an explanation of the terms used in this section, see attributes(7).
SUSv2 and POSIX.1-2001 contain text about overflow (which
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 (respectively,
1024), and the number of mantissa bits 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) instead.
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Copyright 2001 Andries Brouwer <aebcwi.nl>.
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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