private void calculatePoints()
        {
            Computator cmp = new Computator();

            for (int n = 0; n < _mathList.getOperands().Count; n++)
            {
                double x, y;
                string funcName = ((Variable)_mathList.getOperands()[n]).getValue();
                double start    = ((Number)_interval.getOperands()[0]).getValue();

                for (int j = 0; j < stepCount; j++)
                {
                    List <IExpressionType> lst = new List <IExpressionType>();
                    lst.Add(new Number(start));
                    Function tm = new Function(Types.FuncExpression, lst, funcName);

                    x = start;
                    y = ((Number)tm.doOperation(cmp)).getValue();

                    start += step;

                    _pointsArrays[n].Add(new DataPoint(x, y));
                }
            }
        }
        public PlotModel(MathList mathList, Variable var, Interval interval)
        {
            _pointsArrays = new List <DataPoint> [mathList.getOperands().Count];
            for (int p = 0; p < _pointsArrays.Length; p++)
            {
                _pointsArrays[p] = new List <DataPoint>();
            }
            _mathList = mathList;
            _variable = var;

            _interval = interval;
            double length = ((Number)_interval.getOperands()[1]).getValue()
                            - ((Number)_interval.getOperands()[0]).getValue();

            step = length / stepCount;

            calculatePoints();
        }