operator.cs

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using System;
using System.Collections.Generic;
using System.Text;

/// <summary>
/// 运算符类，作为一种扩展性，独立封装
/// </summary>
class Operator
{
    /// <summary>
    /// 运算符
    /// </summary>
    public char Symbol;
    /// <summary>
    /// 是否有交换律
    /// </summary>
    public bool Exchangable;
    /// <summary>
    /// 优先级,值越大越有效
    /// </summary>
    public int Priority;

    public Operator(char symbol, bool exchangable, int priority)
    {
        Symbol = symbol;
        Exchangable = exchangable;
        Priority = priority;
    }
    public static Operator Add = new Operator('+', true, 0);
    public static Operator Sub = new Operator('-', false, 0);
    public static Operator Mul = new Operator('*', true, 1);
    public static Operator Div = new Operator('/', false, 1);
    static List<Operator> operators = null;
    public static List<Operator> Operators
    {
        get
        {
            if (operators == null)
            {
                operators = new List<Operator>(4);
                operators.Add(Add);
                operators.Add(Sub);
                operators.Add(Mul);
                operators.Add(Div);
            }
            return operators;
        }
    }

    public override string ToString()
    {
        return Symbol.ToString();
    }
}