; factorial_long.asm  test with test_factorial_long.c main program
; // factorial_long.c  the simplest example of a recursive function
; //                   a recursive function is a function that calls itself
; long int factorial_long(long int n) // n! is n factorial = 1*2*...*(n-1)*n
; {
;   if( n <= 1 ) return 1;            // must have a way to stop recursion
;   return n * factorial_long(n-1);   // factorial calls factorial with n-1
; }				      // n * (n-1) * (n-2) * ... * (1)
;                                     // note: "C" makes 1 be 1l  long
	global	factorial_long
	section .text
factorial_long:			; extreamly efficient version
	mov	rax, 1		; default return
	cmp	rdi, 1		; compare n to 1
	jle	done

	; normal case n * factorial_long(n-1)
	push	rdi		; save n for multiply
	sub	rdi, 1		; n-1
	call	factorial_long	; rax has factorial_long(n-1)
	pop	rdi
	imul	rax,rdi		; ??
				; n*factorial_long(n-1) in rax
done:	ret			; return with result in rax
; end factorial_long.asm