begin parsing line numbers at start of lines

c64/basic/basic_main_loop.s

@@ -44,13 +44,38 @@ rsl_l1:	lda $0200,x
 	dec tokenise_work1
 	;; Stop trying to rim if we run out of input
 	bne remove_leading_spaces
-*
-	
+*	
 	;; Do printing of the new line
 	lda #$0d
 	jsr $ffd2
 
 	jsr tokenise_line	
+
+	;; Has the user entered a line of BASIC beginning with a number?
+	lda $0200
+	cmp #$30
+	bcc not_a_line
+	cmp #$39
+	bcs not_a_line
+
+	;; Yes, the line begins with a number.
+	;; Parse the line number and check validity
+	inc $d020
+
+	;; injest_number follows tokenise_work1 as the offset into the line,
+	;; so remember the line length somewhere else for now.
+	lda tokenise_work1
+	sta tokenise_work2
+	lda #$00
+	sta tokenise_work1
+	
+	jsr injest_number
+
+	lda tokenise_work1
+	sta $0427
+	
+	
+not_a_line:	
 	
 	jsr ready_message