include "misc.coh";

var fp: int16;

sub factorial(n: int16): (ret: int16) is
	var tmp: int16;

	if n == 1 then
		ret := 1;
	else
		# ret := n * factorial(n - 1);
		@asm "ld hl,(", n, ")";
		@asm "push hl";
		n := n - 1;
		@asm "ld hl,(", n, ")";
		@asm "ld ix,(", fp, ")";
		@asm "ld de, 1f";
		@asm "push de";
		@asm "jp (ix)";
		@asm "1:";
		@asm "ld (", tmp, "),hl"; #tmp = factorial(n-1)
		@asm "pop hl";
		@asm "ld (", n, "),hl";
		ret := n * tmp;
	end if;
end sub;

#setup pointer to factorial
@asm "ld hl,", factorial;
@asm "ld (", fp, "),hl";

print_i16(factorial(5));