Function: calcFunc-dfact

calcFunc-dfact is an autoloaded and byte-compiled function defined in calc-comb.el.gz.

Signature

(calcFunc-dfact N)

Source Code

;; Defined in /usr/src/emacs/lisp/calc/calc-comb.el.gz
(defun calcFunc-dfact (n)   ; [I I] [F F] [Public]
  (cond ((Math-integer-negp n)
	 (if (math-oddp n)
	     (if (eq n -1)
		 1
	       (math-div (if (eq (math-mod n 4) 3) 1 -1)
			 (calcFunc-dfact (math-sub -2 n))))
	   (list 'calcFunc-dfact n)))
	((Math-zerop n) 1)
	((integerp n) (math-double-factorial-iter n (+ 2 (% n 2)) 1 2))
	((math-messy-integerp n)
	 (let ((temp (math-trunc n)))
	   (math-inexact-result)
	   (if (natnump temp)
	       (if (Math-lessp temp 200)
		   (math-with-extra-prec 1
		     (math-double-factorial-iter temp (+ 2 (% temp 2))
						 '(float 1 0) 2))
		 (let* ((half (math-div2 temp))
			(even (math-mul (math-pow 2 half)
					(calcFunc-fact (math-float half)))))
		   (if (math-evenp temp)
		       even
		     (math-div (calcFunc-fact n) even))))
	     (list 'calcFunc-dfact n))))
	((equal n '(var inf var-inf)) n)
	(t (calc-record-why 'natnump n)
	   (list 'calcFunc-dfact n))))