TITLE	"babbage.a difference engine"

;	givens

Y0	=	0	; initial value of y
Delta	=	6	; first difference
Delta2	=	-4	; second difference
Delta3	=	1	; third difference

	USE	"hawk.macs"
	USE	"monitor.h"
	S	START
	EXT	UNUSED
START:
	LIL	R2, UNUSED
	LIL	R1, DSPINI
	JSRS	R1, R1

; In all code that follows
;	R8 is Y
;	R9 is D, the first difference
;	R10 is D2, the second difference
;	R11 is i, the the loop iterator

	LIL	R8, Y0		; y = y0
	LIL	R9, Delta	; d = Delta
	LIL	R10, Delta2	; d2 = Delta2

	LIL	R11,1		; i = 1
LOOP:				; while (i < 10) {
	CMPI	R11,10
	BGE	LOOPX

	MOVE	R3, R8		;    -- param y
	LIS 	R4, 5		;    -- param 5
	LIL	R1, DSPDEC
	JSRS	R1, R1		;    call dspdec(y, 5)
	
	ADD	R8, R8, R9	;    y = y + d
	ADD	R9, R9, R10	;    d = d + d2
	ADDI	R10, R10, Delta3;    d2 = d2 + Delta3

	ADDSI	R11,1		;    i = i + 1
	BR	LOOP		; }
LOOPX:

	LIL	R1,EXIT
	JSRS	R1,R1
	END