为什么std :: pair暴露成员变量？ [英] Why does std::pair expose member variables?

问题描述

从 http://www.cplusplus.com/reference/utility/pair/ ，我们知道 std :: pair 有两个成员变量，第一和第二第一个和

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解决方案

对于原始的C ++ 03 std :: pair

从C ++ 11和更高版本开始（我们现在使用C ++ 14，使用C ++ 17 ） std :: pair 是 std :: tuple 的特殊情况，其中 std :: tuple 可以有任意数量的项目。因此，具有参数化的getter是有意义的，因为发明和标准化任意数量的项目名称是不切实际的。因此，您可以使用 std :: get std :: pair 。

所以，设计的原因是历史的， std :: pair 是向更通用性演变的最终结果。

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; 据我所知，如果封装两个成员变量并给出 getFirst（）; 和 getSecond ）

不，这是垃圾。

这就像说，锤子总是更好，无论你是在钉子，螺丝紧固，或修剪一块木头。特别是在最后一种情况下，锤子不是一个有用的工具。锤子可以是非常有用的，但这并不意味着他们是更好的一般来说：这只是废话。

From http://www.cplusplus.com/reference/utility/pair/, we know that std::pair has two member variables, first and second.

Why did the STL designers decide to expose two member variables, first and second, instead of offering a getFirst() and a getSecond()?

解决方案

For the original C++03 std::pair, functions to access the members would serve no useful purpose.

As of C++11 and later (we're now at C++14, with C++17 coming up fast) std::pair is a special case of std::tuple, where std::tuple can have any number of items. As such it makes sense to have a parameterized getter, since it would be impractical to invent and standardize an arbitrary number of item names. Thus you can use std::get also for a std::pair.

So, the reasons for the design are historical, that the current std::pair is the end result of an evolution towards more generality.

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In other news:

regarding

” As far as I know, it will be better if encapsulating two member variables above and give a getFirst(); and getSecond()

no, that's rubbish.

That's like saying a hammer is always better, whether you're driving in nails, fastening with screws, or trimming a piece of wood. Especially in the last case a hammer is just not a useful tool. Hammers can be very useful, but that doesn't mean that they're “better” in general: that's just nonsense.

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