解释器模式
给定一个语言,定义它的文法的一种表示,并定义一个解释器,这个解释器使用该表示来解释语言中的句子
csharp
// 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(InterpreterContext context)
{
if (context.Statement.Length == 0)
{
return;
}
foreach (var key in Table.Keys)
{
var value = Table[key];
if (context.Statement.EndsWith(key + GetPostFix()))
{
context.Data += value * Multiplier();
context.Statement = context.Statement.Substring(0, context.Statement.Length - 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 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;
}
}
//环境上下文
public sealed class InterpreterContext
{
public InterpreterContext(string statement)
{
Statement = statement;
}
public string Statement { get; set; }
public int Data { get; set; }
}
调用:
csharp
const string roman = "六千四百五十二";
var interpreterContext = new InterpreterContext(roman);
var tree = new ArrayList
{
new GeExpression(),
new ShiExpression(),
new BaiExpression(),
new QianExpression()
};
foreach (Expression exp in tree)
{
exp.Interpreter(interpreterContext);
}
Console.Write(interpreterContext.Data);