public String GetPreviousLine(int pindex) {

        int tindex = pindex;
        while ((tindex > 0 )&& (iExpr.toCharArray()[tindex] != '\n')) {
            tindex--;
        }

        if (iExpr.toCharArray()[tindex] == '\n') {
            tindex--;
        } else {
            return "";
        }

        while ((tindex > 0) && (iExpr.toCharArray()[tindex] != '\n')) {
            tindex--;
        }


        if (iExpr.toCharArray()[tindex] == '\n') {
            tindex--;
        }


        String CurrentLine = "";

        while (tindex < length && (iExpr.toCharArray()[tindex] != '\n')) {
            CurrentLine = CurrentLine + iExpr.toCharArray()[tindex];
            tindex++;
        }

        return CurrentLine + "\n";



    }