double ceil(doublex);
float ceilf(floatx);
long double ceill(long doublex);

DESCRIPTION

These functions shall compute the smallest integral value not less
than x.

An application wishing to check for error situations should set errno
to zero and call
feclearexcept(FE_ALL_EXCEPT) before calling these functions.
On return, if errno is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.

RETURN VALUE

Upon successful completion, ceil(), ceilf(), and ceill()
shall return the smallest integral value not less
than x, expressed as a type double, float, or long
double, respectively.

If
x is NaN, a NaN shall be returned.

If x is ±0 or ±Inf, x shall be returned.

If the correct value would cause overflow, a range error shall occur
and ceil(), ceilf(), and ceill() shall
return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
respectively.

ERRORS

These functions shall fail if:

Range Error

The result overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow floating-point exception shall be raised.

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

The integral value returned by these functions need not be expressible
as an int or long. The return value should
be tested before assigning it to an integer type to avoid the undefined
results of an integer overflow.

The ceil() function can only overflow when the floating-point
representation has DBL_MANT_DIG > DBL_MAX_EXP.

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
& MATH_ERREXCEPT) are independent of
each other, but at least one of them must be non-zero.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

feclearexcept() , fetestexcept() , floor() , isnan()
, the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions
for
Mathematical Functions, <math.h>

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .