Data commit

Task/Determine-if-a-string-is-numeric/6502-Assembly/determine-if-a-string-is-numeric.6502

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+*=$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