public ArithmExprEvaluator(AdditionSubtractionEvaluator l) { expr = l; }
public AdditionSubtractionEvaluator(AdditionSubtractionEvaluator l, MultiplicationDivisionEvaluator r, string op) { left = new MultiplicationDivisionEvaluator(new ArithmValueEvaluator(new ArithmExprEvaluator(l))); right = r; arithmOperator = op; }