The 'ceiling' function
truncates an integer or
(defun ceiling (number) (let ((trunc (truncate number))) (if (or (minusp number) (= number trunc)) trunc (1+ trunc))))
The 'ceiling' function computes an integer number that has
been truncated toward positive infinity.
Examples:
(ceiling 3) => 3 (ceiling -3) => -3 (ceiling 3.0) => 3 (ceiling -3.0) => -3 (ceiling 3.1) => 4 (ceiling -3.1) => -3 (ceiling 3.5) => 4 (ceiling -3.5) => -3 (ceiling 3.9) => 4 (ceiling -3.9) => -3 (ceiling 4.0) => 4 (ceiling -4.0) => -4