.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "CEIL" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" ceil 
.SH NAME
ceil, ceilf, ceill \- ceiling value function
.SH SYNOPSIS
.LP
\fB#include <math.h>
.br
.sp
double ceil(double\fP \fIx\fP\fB);
.br
float ceilf(float\fP \fIx\fP\fB);
.br
long double ceill(long double\fP \fIx\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
These functions shall compute the smallest integral value not less
than \fIx\fP.
.LP
An application wishing to check for error situations should set \fIerrno\fP
to zero and call
\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
On return, if \fIerrno\fP is non-zero or
\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.
.SH RETURN VALUE
.LP
Upon successful completion, \fIceil\fP(), \fIceilf\fP(), and \fIceill\fP()
shall return the smallest integral value not less
than \fIx\fP, expressed as a type \fBdouble\fP, \fBfloat\fP, or \fBlong
double\fP, respectively.
.LP
If
\fIx\fP is NaN, a NaN shall be returned.
.LP
If \fIx\fP is \(+-0 or \(+-Inf, \fIx\fP shall be returned. 
.LP
If the correct value would cause overflow, a range error shall occur
and \fIceil\fP(), \fIceilf\fP(), and \fIceill\fP() shall
return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
respectively. 
.SH ERRORS
.LP
These functions shall fail if:
.TP 7
Range\ Error
The result overflows. 
.LP
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then \fIerrno\fP 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.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
The integral value returned by these functions need not be expressible
as an \fBint\fP or \fBlong\fP. The return value should
be tested before assigning it to an integer type to avoid the undefined
results of an integer overflow.
.LP
The \fIceil\fP() function can only overflow when the floating-point
representation has DBL_MANT_DIG > DBL_MAX_EXP.
.LP
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.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIfloor\fP() , \fIisnan\fP()
, the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions
for
Mathematical Functions, \fI<math.h>\fP
.SH 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 .