floor(3) Library Functions Manual floor(3) NAME floor, floorf, floorl - largest integral value not greater than argu- ment LIBRARY Math library (libm, -lm) SYNOPSIS #include <math.h> double floor(double x); float floorf(float x); long double floorl(long double x); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): floorf(), floorl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE DESCRIPTION These functions return the largest integral value that is not greater than x. For example, floor(0.5) is 0.0, and floor(-0.5) is -1.0. RETURN VALUE These functions return the floor of x. If x is integral, +0, -0, NaN, or an infinity, 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 at- tributes(7). ┌────────────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├────────────────────────────────────────────┼───────────────┼─────────┤ │floor(), floorf(), floorl() │ Thread safety │ MT-Safe │ └────────────────────────────────────────────┴───────────────┴─────────┘ STANDARDS C99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD. NOTES SUSv2 and POSIX.1-2001 contain text about overflow (which might set er- rno 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 mantis- sa 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 (re- spectively, 53).) SEE ALSO ceil(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3) Linux man-pages 6.03 2023-02-05 floor(3)
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