.Net行为型设计模式之解释器模式（Interpreter）

static void Main(string[] args)
{
    string roman = "五亿七千三百零二万六千四百五十二";
    //分解：((五)亿)((七千)(三百)(零)(二)万)
    //((六千)(四百)(五十)(二))

    Context context = new Context(roman);
    ArrayList tree = new ArrayList();

    tree.Add(new GeExpression());
    tree.Add(new ShiExpression());
    tree.Add(new BaiExpression());
    tree.Add(new QianExpression());
    tree.Add(new WanExpression());
    tree.Add(new YiExpression());

    foreach (Expression exp in tree)
    {
        exp.Interpreter(context);
    }

    Console.Write(context.Data);
}
// 抽象表达式
public abstract class Expression
{
    protected Dictionary<string, int> table = new Dictionary<string, int>(9);

    protected Expression()
    {
        table.Add("一", 1);
        table.Add("二", 2);
        table.Add("三", 3);
        table.Add("四", 4);
        table.Add("五", 5);
        table.Add("六", 6);
        table.Add("七", 7);
        table.Add("八", 8);
        table.Add("九", 9);
    }

    public virtual void Interpreter(Context context)
    {
        if (context.Statement.Length == 0)
        {
            return;
        }

        foreach (string key in table.Keys)
        {
            int value = table[key];

            if (context.Statement.EndsWith(key + GetPostFix()))
            {
                context.Data += value * this.Multiplier();
                context.Statement = context.Statement.Substring(0, context.Statement.Length - this.GetLength());
            }
            if (context.Statement.EndsWith("零"))
            {
                context.Statement = context.Statement.Substring(0, context.Statement.Length - 1);
            }
        }
    }

    public abstract string GetPostFix();

    public abstract int Multiplier();

    //这个可以通用，但是对于个位数字例外，所以用虚方法
    public virtual int GetLength()
    {
        return this.GetPostFix().Length + 1;
    }
}

//个位表达式
public sealed class GeExpression : Expression
{
    public override string GetPostFix()
    {
        return "";
    }

    public override int Multiplier()
    {
        return 1;
    }

    public override int GetLength()
    {
        return 1;
    }
}

//十位表达式
public sealed class ShiExpression : Expression
{
    public override string GetPostFix()
    {
        return "十";
    }

    public override int Multiplier()
    {
        return 10;
    }
}

//百位表达式
public sealed class BaiExpression : Expression
{
    public override string GetPostFix()
    {
        return "百";
    }

    public override int Multiplier()
    {
        return 100;
    }
}

//千位表达式
public sealed class QianExpression : Expression
{
    public override string GetPostFix()
    {
        return "千";
    }

    public override int Multiplier()
    {
        return 1000;
    }
}

//万位表达式
public sealed class WanExpression : Expression
{
    public override string GetPostFix()
    {
        return "万";
    }

    public override int Multiplier()
    {
        return 10000;
    }

    public override void Interpreter(Context context)
    {
        if (context.Statement.Length == 0)
        {
            return;
        }

        ArrayList tree = new ArrayList();

        tree.Add(new GeExpression());
        tree.Add(new ShiExpression());
        tree.Add(new BaiExpression());
        tree.Add(new QianExpression());

        foreach (string key in table.Keys)
        {
            if (context.Statement.EndsWith(GetPostFix()))
            {
                int temp = context.Data;
                context.Data = 0;

                context.Statement = context.Statement.Substring(0, context.Statement.Length - this.GetLength());

                foreach (Expression exp in tree)
                {
                    exp.Interpreter(context);
                }
                context.Data = temp + context.Data * this.Multiplier();
            }
        }
    }
}

//亿位表达式
public sealed class YiExpression : Expression
{
    public override string GetPostFix()
    {
        return "亿";
    }

    public override int Multiplier()
    {
        return 100000000;
    }

    public override void Interpreter(Context context)
    {
        ArrayList tree = new ArrayList();

        tree.Add(new GeExpression());
        tree.Add(new ShiExpression());
        tree.Add(new BaiExpression());
        tree.Add(new QianExpression());

        foreach (string key in table.Keys)
        {
            if (context.Statement.EndsWith(GetPostFix()))
            {
                int temp = context.Data;
                context.Data = 0;
                context.Statement = context.Statement.Substring(0, context.Statement.Length - this.GetLength());

                foreach (Expression exp in tree)
                {
                    exp.Interpreter(context);
                }
                context.Data = temp + context.Data * this.Multiplier();
            }
        }
    }
}

//环境上下文
public sealed class Context
{
    private string _statement;
    private int _data;

    public Context(string statement)
    {
        this._statement = statement;
    }

    public string Statement
    {
        get { return this._statement; }
        set { this._statement = value; }
    }

    public int Data
    {
        get { return this._data; }
        set { this._data = value; }
    }
}