CEIL(P) POSIX Programmer s Manual CEIL(P)

PROLOG This manual page is part of the POSIX Programmer s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME ceil, ceilf, ceill - ceiling value function

SYNOPSIS #include <math.h>

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

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 dou- ble, 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 represen- tation 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 Defini- tions 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 .

IEEE/The Open Group 2003 CEIL(P)