亚洲私拍自拍,欧美在线免费视频,精品1区2区3区4区

名稱	Interpreter
結構
意圖	給定一個語言，定義它的文法的一種表示，并定義一個解釋器，這個解釋器使用該表示來解釋語言中的句子。
適用性	當有一個語言需要解釋執行, 并且你可將該語言中的句子表示為一個抽象語法樹時，可使用解釋器模式。而當存在以下情況時該模式效果最好：該文法簡單對于復雜的文法, 文法的類層次變得龐大而無法管理。此時語法分析程序生成器這樣的工具是更好的選擇。它們無需構建抽象語法樹即可解釋表達式, 這樣可以節省空間而且還可能節省時間。效率不是一個關鍵問題最高效的解釋器通常不是通過直接解釋語法分析樹實現的, 而是首先將它們轉換成另一種形式。例如，正則表達式通常被轉換成狀態機。但即使在這種情況下, 轉換器仍可用解釋器模式實現, 該模式仍是有用的。

Code Example

namespace?Interpreter_DesignPattern

{

????using?System;

????using?System.Collections;

????class?Context?

????{

????????

????}

????abstract?class?AbstractExpression?

????{

????????abstract?public?void?Interpret(Context?c);

????}

????//?class?for?terminal?symbol

????class?TerminalExpression?:?AbstractExpression

????{

????????override?public?void?Interpret(Context?c)????

????????{

????????????

????????}

????}

????//?class?for?grammar?rule?(one?per?rule?needed)

????class?NonterminalExpression?:?AbstractExpression

????{

????????override?public?void?Interpret(Context?c)????

????????{

????????????

????????}????

????}

????//?to?extend?grammar,?just?add?other?NonterminalExpression?classes

????///?<summary>

????///????Summary?description?for?Client.

????///?</summary>

????public?class?Client

????{

????????public?static?int?Main(string[]?args)

????????{

????????????Context?c?=?new?Context();

????????????ArrayList?l?=?new?ArrayList();?//really?need?a?tree?here!

????????????//?build?up?context?information?

????????????//?.?.?.

????????????//?Populate?abstract?syntax?tree?with?data

????????????l.Add(new?TerminalExpression());

????????????l.Add(new?NonterminalExpression());

????????????//?interpret

????????????foreach?(AbstractExpression?exp?in?l)

????????????{

????????????????exp.Interpret(c);

????????????}

????????????????????

????????????return?0;

????????}

????}

}

解析表達式:

//?Interpreter?pattern?--?Real?World?example??

using?System;

using?System.Collections;

namespace?DoFactory.GangOfFour.Interpreter.RealWorld

{

??//?MainApp?test?application?

??class?MainApp

??{

????static?void?Main()

????{

??????string?roman?=?"MCMXXVIII";

??????Context?context?=?new?Context(roman);

??????//?Build?the?'parse?tree'?

??????ArrayList?tree?=?new?ArrayList();

??????tree.Add(new?ThousandExpression());

??????tree.Add(new?HundredExpression());

??????tree.Add(new?TenExpression());

??????tree.Add(new?OneExpression());

??????//?Interpret?

??????foreach?(Expression?exp?in?tree)

??????{

????????exp.Interpret(context);

??????}

??????Console.WriteLine("{0}?=?{1}",?

????????roman,?context.Output);

??????//?Wait?for?user?

??????Console.Read();

????}

??}

??//?"Context"?

??class?Context

??{

????private?string?input;

????private?int?output;

????//?Constructor?

????public?Context(string?input)

????{

??????this.input?=?input;

????}

????//?Properties?

????public?string?Input

????{

??????get{?return?input;?}

??????set{?input?=?value;?}

????}

????public?int?Output

????{

??????get{?return?output;?}

??????set{?output?=?value;?}

????}

??}

??//?"AbstractExpression"?

??abstract?class?Expression

??{

????public?void?Interpret(Context?context)

????{

??????if?(context.Input.Length?==?0)?

????????return;

??????if?(context.Input.StartsWith(Nine()))

??????{

????????context.Output?+=?(9?*?Multiplier());

????????context.Input?=?context.Input.Substring(2);

??????}

??????else?if?(context.Input.StartsWith(Four()))

??????{

????????context.Output?+=?(4?*?Multiplier());

????????context.Input?=?context.Input.Substring(2);

??????}

??????else?if?(context.Input.StartsWith(Five()))

??????{

????????context.Output?+=?(5?*?Multiplier());

????????context.Input?=?context.Input.Substring(1);

??????}

??????while?(context.Input.StartsWith(One()))

??????{

????????context.Output?+=?(1?*?Multiplier());

????????context.Input?=?context.Input.Substring(1);

??????}

????}

????public?abstract?string?One();

????public?abstract?string?Four();

????public?abstract?string?Five();

????public?abstract?string?Nine();

????public?abstract?int?Multiplier();

??}

??//?Thousand?checks?for?the?Roman?Numeral?M?

??//?"TerminalExpression"?

??class?ThousandExpression?:?Expression

??{

????public?override?string?One()?{?return?"M";?}

????public?override?string?Four(){?return?"?";?}

????public?override?string?Five(){?return?"?";?}

????public?override?string?Nine(){?return?"?";?}

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

??}

??//?Hundred?checks?C,?CD,?D?or?CM?

??//?"TerminalExpression"?

??class?HundredExpression?:?Expression

??{

????public?override?string?One()?{?return?"C";?}

????public?override?string?Four(){?return?"CD";?}

????public?override?string?Five(){?return?"D";?}

????public?override?string?Nine(){?return?"CM";?}

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

??}

??//?Ten?checks?for?X,?XL,?L?and?XC?

??//?"TerminalExpression"?

??class?TenExpression?:?Expression

??{

????public?override?string?One()?{?return?"X";?}

????public?override?string?Four(){?return?"XL";?}

????public?override?string?Five(){?return?"L";?}

????public?override?string?Nine(){?return?"XC";?}

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

??}

??//?One?checks?for?I,?II,?III,?IV,?V,?VI,?VI,?VII,?VIII,?IX?

??//?"TerminalExpression"?

??class?OneExpression?:?Expression

??{

????public?override?string?One()?{?return?"I";?}

????public?override?string?Four(){?return?"IV";?}

????public?override?string?Five(){?return?"V";?}

????public?override?string?Nine(){?return?"IX";?}

????public?override?int?Multiplier()?{?return?1;?}

??}

}

Output

MCMXXVIII = 1928

posted on 2006-01-03 16:02 夢在天涯閱讀(922) 評論(0) 編輯收藏引用所屬分類: Design pattern

只有注冊用戶登錄后才能發表評論。


相關文章: 本博客所有精華隨筆索引策略模式（policy）設計模式隨筆分類 MFC與設計模式接口模式 -- 接口中為什么不能包含delegate .net中更好的使用設計模式的DLL(Commonly Used .NET Coding Patterns in CodeDom)(轉) 模式設計c#－－行為型－－visitor 模式設計c#－－行為型－－strategy 模式設計c#－－行為型－－state 模式設計c#－－行為型－－observer

網站導航: 博客園 IT新聞 BlogJava 博問 Chat2DB 管理

青青草原综合久久大伊人导航_色综合久久天天综合_日日噜噜夜夜狠狠久久丁香五月_热久久这里只有精品

C++ Programmer's Cookbook

模式設計c#－－行為型－－interpreter

公告

導航

統計

常用鏈接

隨筆分類

隨筆檔案

收藏夾

Blogs

c#(csharp)

C++(cpp)

Enlish

Forums(bbs)

My self

Often go

Useful Webs

Xml/Uml/html

搜索

積分與排名

最新評論

閱讀排行榜