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Bir metnin geçerli bir isbn numarası olup olmadığının kontrol edilmesi

function IsISBN(ISBN: string): Boolean; var Number, CheckDigit: string; CheckValue, CheckSum, Err: Integer; i, Cnt: Word; begin // Get check digit CheckDigit := Copy(ISBN, Length(ISBN), 1); // Get rest of ISBN, minus check digit and its hyphen Number := Copy(ISBN, 1, Length(ISBN) - 2); // Length of ISBN remainder must be 11 and check digit between 9 and 9 or X if (Length(Number) = 11) and (Pos(CheckDigit, '0123456789X') > 0) then begin // Get numeric value for check digit if (CheckDigit = 'X') then CheckSum := 10 else Val(CheckDigit, CheckSum, Err); // Iterate through ISBN remainder, applying decode algorithm Cnt := 1; for i := 1 to 12 do begin // Act only if current character is between "0" and "9" to exclude hyphens if (Pos(Number[i], '0123456789') > 0) then begin Val(Number[i], CheckValue, Err); // Algorithm for each character in ISBN remainder, Cnt is the nth character // so processed CheckSum := CheckSum + CheckValue * (11 - Cnt); Inc(Cnt); end; end; // Verify final value is evenly divisible by 11 if (CheckSum mod 11 = 0) then IsISBN := True else IsISBN := False; end else IsISBN := False; end; // Kullanımı procedure TForm1.Button1Click(Sender: TObject); begin // '975-93527-0-2': Delphi Programcılığı ve SQL ISBN if IsISBN(Edit1.Text) then ShowMessage('Geçerli') else ShowMessage('Geçersiz'); end;