plucky (3) ceil.3.gz

NAME

       ceil, ceilf, ceill - ceiling function: smallest integral value not less than argument

LIBRARY

       Math library (libm, -lm)

SYNOPSIS

       #include <math.h>

       double ceil(double x);
       float ceilf(float x);
       long double ceill(long double x);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       ceilf(), ceill():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       These functions return the smallest integral value that is not less than x.

       For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.

RETURN VALUE

       These functions return the ceiling of x.

       If x is integral, +0, -0, NaN, or infinite, x itself is returned.

ERRORS

       No errors occur.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                                     │ Attribute     │ Value   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ceil(), ceilf(), ceill()                                                      │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       C99, POSIX.1-2001.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

       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  was  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).)  This was removed in POSIX.1-2008.

       The integral value returned by these functions may be too large to store in an integer type  (int,  long,
       etc.).  To avoid an overflow, which will produce undefined results, an application should perform a range
       check on the returned value before assigning it to an integer type.

SEE ALSO

       floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)