*=$0801
	db $0E,$08,$0A,$00,$9E,$20,$28,$32,$30,$36,$34,$29,$00,$00,$00  ;required init code on commodore 64 floppy disks
*=$0810

	lda #$0e
	jsr chrout ;required for my printing routine to work.

z_HL equ $02
z_L  equ $02
z_H  equ $03
z_B  equ $04
	
	
	
	loadpair z_HL,TestString0
	jsr isStringNumeric
	
	loadpair z_HL,TestString1
	jsr isStringNumeric
	
	loadpair z_HL,TestString2
	jsr isStringNumeric
	
	loadpair z_HL,TestString3
	jsr isStringNumeric	

	loadpair z_HL,TestString4
	jsr isStringNumeric
	
	loadpair z_HL,TestString5
	jsr isStringNumeric
	
	loadpair z_HL,TestString6
	jsr isStringNumeric
	
	loadpair z_HL,TestString7
	jsr isStringNumeric	
	
	loadpair z_HL,TestString8
	jsr isStringNumeric	
	rts				;return to basic

isStringNumeric:
; input: z_HL = source address
	pushY
		ldy #0
		sty z_B		;our tally for decimal points
		
checkFirstChar:
		lda (z_HL),y
		beq notNumeric			;a null string is not a valid number!
		cmp #'-'
		beq isNegative_OK
		cmp #'.'
		beq isFloat_OK
		and #$30
		cmp #$30
		beq isNumeral_OK
		;else, is not numeric
notNumeric:
	popY
	jsr PrintString_TextScreen	;prints what's already in z_HL
	jsr NewLine	
	loadpair z_HL,isStringNumeric_Fail
	jsr PrintString_TextScreen
	jsr NewLine
	jmp NewLine
	;rts
isNegative_OK:
isNumeral_OK:
		iny
		jmp loop_isStringNumeric
isFloat_OK:
		iny
		inc z_B
loop_isStringNumeric:
		lda (z_HL),y
		beq Terminated_isStringNumeric
		cmp #'.'
		beq CheckIfDecimalAlreadyOccurred
		and #$30
		cmp #$30
		bne notNumeric
loop_overhead_isStringNumeric:
		iny
		jmp loop_isStringNumeric
		
CheckIfDecimalAlreadyOccurred:
		lda z_B
		bne notNumeric
		inc z_B
		jmp loop_overhead_isStringNumeric
		
Terminated_isStringNumeric:
;if we got this far the string is numeric.
	popY
	jsr PrintString_TextScreen	;prints what's already in z_HL
	jsr NewLine	
	loadpair z_HL,isStringNumeric_Pass
	jsr PrintString_TextScreen
	jsr NewLine
	jmp NewLine
	;rts
	
isStringNumeric_Pass:
	db "IS NUMERIC",0
isStringNumeric_Fail:
	db "IS NOT NUMERIC",0
	
TestString0:
	db 0
TestString1:
	db "123",0
TestString2:
	db "-30",0
TestString3:
	db "123.45",0
TestString4:
	db "-123.45",0
TestString5:
	db "ABCDE",0
TestString6:
	db "-34-5",0
TestString7:
	db "1.000.000",0
TestString8:
	db ".23456",0