feat(catalan): Implement divison with accumulator subroutine

1 files changed, 36 insertions, 4 deletions

diff --git a/catalan/catalan.a65 b/catalan/catalan.a65
index 3dd3168..53d30eb 100644
--- a/catalan/catalan.a65
+++ b/catalan/catalan.a65
@@ -44,10 +44,12 @@ cat_n	.byt 1
 n	.byt 0
 
 main
-	lda #3
-	sta multa_arg1
-	lda #14
-	jsr multa
+	lda #9
+	sta diva_arg1
+	lda #144
+	jsr diva
+	clc
+	adc #49
 	putchar()
 	rts
 
@@ -85,6 +87,36 @@ arg1		.byt 0
 addend		.byt 0
 .)
 
+// a /= diva_arg1
+diva .(
+	ora #0		; Update flags, so they're accurate with the accumulator value
+	beq return	; if (a == 0) return a
+
+	ldx arg1	; x = arg1
+	cpx #0		; if (x == 0)
+	beq r_zero	;   return 0
+	cpx #1		; if (x == 1)
+	beq return	;   return a
+
+	stx subtrahend	; subtrahend = x
+	ldx #0		; x = 0
+loop	sec		; do  carry = 1
+	sbc subtrahend	;     a -= addend + !carry
+	inx		;     ++x
+	cmp subtrahend	; while (a >= subtrahend)
+	bcs loop
+
+return	txa
+	rts
+
+r_zero	lda #0
+	rts
+
++diva_arg1
+arg1		.byt 0
+subtrahend	.byt 0
+.)
+
 buffer	.byt 0
 
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