我的意思是,除了它的名字标准模板库(后来演变成c++标准库)。

c++最初将面向对象的概念引入到C中,也就是说:您可以根据特定实体的类和类层次结构来判断它能做什么和不能做什么(不管它是如何做的)。由于多重继承的复杂性,一些能力的组合更难以用这种方式描述,而且c++以一种有点笨拙的方式支持仅接口继承(与java等相比),但它确实存在(并且可以改进)。

然后模板开始发挥作用,还有STL。STL似乎采用了经典的OOP概念,并将它们冲入下水道,取而代之的是使用模板。

当模板用于泛化类型时,类型本身与模板的操作无关(例如容器),这两种情况之间应该有区别。vector<int>非常有意义。

然而,在许多其他情况下(迭代器和算法),模板化类型应该遵循一个“概念”(Input Iterator, Forward Iterator,等等),其中概念的实际细节完全由模板函数/类的实现定义,而不是由模板使用的类型的类定义,这在某种程度上是对OOP的反使用。

例如,你可以告诉函数:

void MyFunc(ForwardIterator<...> *I);

更新:由于在最初的问题中不清楚,ForwardIterator本身可以被模板化以允许任何ForwardIterator类型。相反,将ForwardIterator作为一个概念。

只有通过查看它的定义才能期望Forward Iterator,在这里你需要查看以下方面的实现或文档:

template <typename Type> void MyFunc(Type *I);

我可以提出两个主张来支持使用模板:通过为每个使用的类型重新编译模板,而不是使用动态分派(主要通过虚表),可以使编译后的代码更加高效。2. 事实上,模板可以与原生类型一起使用。

然而,我正在寻找一个更深刻的原因,放弃经典的面向对象的支持模板的STL?


当前回答

“面向对象编程对我来说只意味着消息传递、状态过程的本地保留、保护和隐藏,以及所有事情的极端后期绑定。它可以在Smalltalk和LISP中完成。可能还有其他系统也有这种可能,但我不知道它们。”——Alan Kay (Smalltalk的创造者)

c++、Java和大多数其他语言都与经典的OOP相去甚远。也就是说,为意识形态争论并不是特别有效。c++在任何意义上都不是纯粹的,所以它实现的功能在当时似乎是有实用意义的。

其他回答

如何与ForwardIterator*进行比较?也就是说,你如何检查你所拥有的物品是否是你正在寻找的,或者你已经错过了它?

大多数时候,我会使用这样的方法:

void MyFunc(ForwardIterator<MyType>& i)

这意味着我知道I指向MyType的,我知道如何比较它们。虽然它看起来像一个模板,但实际上不是(没有“template”关键字)。

最基本的问题是

void MyFunc(ForwardIterator *I);

你如何安全地获取迭代器返回的东西的类型?对于模板,这是在编译时为您完成的。

我的理解是,Stroustrup最初更喜欢“oop风格”的容器设计,实际上也没有看到其他的方法。Alexander Stepanov是STL的负责人,他的目标并不包括“使它面向对象”:

That is the fundamental point: algorithms are defined on algebraic structures. It took me another couple of years to realize that you have to extend the notion of structure by adding complexity requirements to regular axioms. ... I believe that iterator theories are as central to Computer Science as theories of rings or Banach spaces are central to Mathematics. Every time I would look at an algorithm I would try to find a structure on which it is defined. So what I wanted to do was to describe algorithms generically. That's what I like to do. I can spend a month working on a well known algorithm trying to find its generic representation. ... STL, at least for me, represents the only way programming is possible. It is, indeed, quite different from C++ programming as it was presented and still is presented in most textbooks. But, you see, I was not trying to program in C++, I was trying to find the right way to deal with software. ... I had many false starts. For example, I spent years trying to find some use for inheritance and virtuals, before I understood why that mechanism was fundamentally flawed and should not be used. I am very happy that nobody could see all the intermediate steps - most of them were very silly.

(在接下来的采访中,他解释了为什么继承和虚拟——也就是面向对象的设计“从根本上存在缺陷,不应该被使用”)。

当Stepanov将他的库展示给Stroustrup时,Stroustrup和其他人付出了巨大的努力,将其纳入ISO c++标准(同一次采访):

The support of Bjarne Stroustrup was crucial. Bjarne really wanted STL in the standard and if Bjarne wants something, he gets it. ... He even forced me to make changes in STL that I would never make for anybody else ... he is the most single minded person I know. He gets things done. It took him a while to understand what STL was all about, but when he did, he was prepared to push it through. He also contributed to STL by standing up for the view that more than one way of programming was valid - against no end of flak and hype for more than a decade, and pursuing a combination of flexibility, efficiency, overloading, and type-safety in templates that made STL possible. I would like to state quite clearly that Bjarne is the preeminent language designer of my generation.

“面向对象编程对我来说只意味着消息传递、状态过程的本地保留、保护和隐藏,以及所有事情的极端后期绑定。它可以在Smalltalk和LISP中完成。可能还有其他系统也有这种可能,但我不知道它们。”——Alan Kay (Smalltalk的创造者)

c++、Java和大多数其他语言都与经典的OOP相去甚远。也就是说,为意识形态争论并不是特别有效。c++在任何意义上都不是纯粹的,所以它实现的功能在当时似乎是有实用意义的。

在对STL作者Stepanov的采访中可以找到答案:

是的。STL不是面向对象的。我 认为面向对象是 几乎和人造的一样是骗局 情报。我还没见过 这段有趣的代码 来自这些面向对象的人。