Item 1:View C++ as a federation of languages
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Item 1:將C++視為語言的聯(lián)合體
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最初,C++僅僅是在C的基礎(chǔ)上附加了一些面向?qū)ο蟮奶卣鳌5牵S著C++的成長發(fā)展,C++已經(jīng)成為了一個多范式的編程語言,一個囊括了過程化,面向?qū)ο螅瘮?shù)化,泛型以及元編程特性的聯(lián)合體。可以將它分成4個部分:
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C
------ 歸根結(jié)底,C++依然是基于C的。模塊,語句,預(yù)處理器,內(nèi)建數(shù)據(jù)類型,數(shù)組,指針等,全都來自于C。只是在很多方面,C++提出了更高級的解決問題的方法。
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Object-Oriented C++
------ C++的這部分就是C with Classes 涉及到的全部:類(包括構(gòu)造函數(shù)和析構(gòu)函數(shù)),封裝,繼承,多態(tài),虛函數(shù)(動態(tài)邦定)等。C++的這一部分直接適用于面向?qū)ο笤O(shè)計的經(jīng)典規(guī)則。
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Template C++
------ 這是C++的泛型編程部分。
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STL
------ STL是一個特殊的模板庫。它將容器,迭代器,算法和函數(shù)對象優(yōu)雅的整合在一起。
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頭腦中保持這四個子語言,從一種子語言轉(zhuǎn)到另一種時,為了高效編程,需要改變策略:
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????? 例如,適用內(nèi)建(類C的)類型時,傳值通常比傳引用更高效,但是當(dāng)從C++的C部分轉(zhuǎn)到C++的Object-Oriented部分,用戶自定義構(gòu)造函數(shù)和析構(gòu)函數(shù)意味著更好的做法是將引用傳遞給const參數(shù)。在 Template C++ 中工作時,這一點更加重要,因為,在這種情況下,你甚至不知道你的操作涉及到的對象的類型。當(dāng)你進入 STL,無論如何,你知道迭代器和函數(shù)對象以 C 的指針為原型,對于 STL 中的迭代器和函數(shù)對象,古老的 C 中的傳值規(guī)則又重新生效。
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Things to Remember:
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????? 高效C++編程規(guī)則的變化,依賴于你使用C++的哪一個部分。
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------------------- English --------------------
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In the beginning, C++ was just C with some object-oriented features tacked on. As the language matured, C++?have become a multiparadigm programming language, one suppoting a combination of procedural, object-oriented, functional, generic, and metaprogramming features.
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There are four parts in the C++:
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C
------ Way down deep, C++ is still based on C. Blocks, statements, the preprocessor, built-in data types, arrays, pointers,etc, all come from C. In many cases, C++ just offers approaches to problems that are superior to their C counterparts.
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Object-Oriented C++
------ This part of C++ is what C with Classes was all about: classes(including constructors and destructors), encapsulation, inheritance, polymorphism, virtual functions(dynamic binding),etc. This is the part of C++ to which the classic rules for object-oriented design most directly apply.
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Template C++
------ This is the generic programming part of C++.
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The STL
------ The STL si avery special template library. Its conventions regarding containers, iterators, algorithms, and function objects mesh beautifully.
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Keep these four sublanguages in mind, and don't be surprised when you encounter situations where effective programming requires that you change strategy when you switch from one sublanguage to another.
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For example, pass-by-value is generally more efficient than pass-by-reference for built-in (i.e., C-like) types, but when you move from the C part of C++ to Object-Oriented C++, the existence of user-defined constructors and destructors means that pass-by-reference-to-const is usually better. This is especially the case when working in Template C++, because there, you don't even know the type of object you're dealing with. When you cross into the STL, however, you know that iterators and function objects are modeled on pointers in C, so for iterators and function objects in the STL, the old C pass-by-value rule applies again.??
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Things to Remember
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Rules for effective C++ programming vary, depending on the part of C++ you are using!
馬嘉楠
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