Data commit

Task/ISBN13-check-digit/Delphi/isbn13-check-digit.delphi

@@ -0,0 +1,37 @@
+function ValidateISBN(ISBN: string): boolean;
+{Validate an ISBN number}
+var I,N,Sum: integer;
+begin
+Sum:=0;
+{Go througha chars, ignoring non-digits}
+for I:=1 to Length(ISBN) do
+ if ISBN[I] in ['0'..'9'] then
+	begin
+	N:=StrToInt(ISBN[I]);
+	{Every other digit multiplied by 3}
+	if (I and 1)=1 then N:=N*3;
+	{Sum digits}
+	Sum:=Sum+N;
+	end;
+{The sum must be an even multiple of 10}
+Result:=(Sum mod 10)=0;
+end;
+
+procedure ValidateAndShow(Memo: TMemo; ISBN: string);
+{Validate ISBN number and show the result}
+var S: string;
+begin
+S:=ISBN;
+if ValidateISBN(ISBN) then S:=S+' (Good)'
+else S:=S+' (Bad)';
+Memo.Lines.Add(S);
+end;
+
+procedure TestISBNSet(Memo: TMemo);
+{Test supplied set of ISBN numbers}
+begin
+ValidateAndShow(Memo,'978-0596528126');		//(good)
+ValidateAndShow(Memo,'978-0596528120');		//(bad)
+ValidateAndShow(Memo,'978-1788399081');		//(good)
+ValidateAndShow(Memo,'978-1788399083');		//(bad)
+end;