Section (3) floor
floor, floorf, floorl — largest integral value not greater than argument
||long double x
These functions return the largest integral value that is
not greater than
floor(0.5) is 0.0, and
These functions return the floor of
x is integral,
+0, −0, NaN, or an infinity,
x itself is returned.
For an explanation of the terms used in this section, see attributes(7).
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
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,
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