什么样的“特质"?在C ++ 0x标准中使用/定义 [英] What kind of "Traits" are used/defined in the C++0x Standard

问题描述

C ++中的特征封装了一系列操作，这些操作允许算法或数据结构以实例化该类型的类型进行操作. char_traits 是将 string -和文件所需功能分组的示例.

A trait in C++ encapsulates a family of operations that allow an Algorithm or Data Structure to operator with that type with which it is instantiated. char_traits are an example for grouping string- and file-required functions.

但并非所有特征的名称中都带有特征"，对吗?我想到了 numeric_limits .这也是特质"吗?即使其中没​​有名称"trait"?

But not all traits have "trait" in their name, right? numeric_limits comes to mind. Is this a "Trait", too? Even without the name "trait" in it?

那么，还有其他可以/应该被认为是特质"的模板吗?除了我发现的示例之外:

So, are there other Templates that could/should be considered a "Trait"? Besides the examples I found:

• allocator_traits 如何获取内存
• pointer_traits 如何间接访问对象
• type_traits 元编程
• char_taits 表示符号序列
• iterator_traits 如何前进，后退和到达元素
• regex_traits 用于...正则表达式.

• allocator_traits how to get memory
• pointer_traits how to access an object indirectly
• type_traits meta programming
• char_taits for sequence of symbols
• iterator_traits how to get forward, backward and to the element
• regex_traits for... regexes.

我想，我要问的是，特征是否有纯定义?

I guess, what I am asking, too, is there a pure definition for traits?

我特别不确定的是:

上面提到的
• numeric_limits
• < chrono> 的自定义特征" [20.11.4]，即 duration_values
• 关于散列有什么意义?函子 hash<> 是否可以视为特征?
• 如果是这样，不是所有需求都是特征"，例如"CopyAssignable"等吗?
• 然后，被遗弃的概念"是最终的特征"-定义吗?

• numeric_limits mentioned above
• <chrono>s customization "traits", [20.11.4], i.e. duration_values
• what about Hashing? Can the functor hash<> be considered to be a trait?
• If thats the case, are not all requirements "traits", like "CopyAssignable", etc?
• And then, are the abandoned "Concepts" the ultimate "trait"-Definition?

更新:这个问题究竟是什么使特质成为特质，这个问题在细节上似乎有点争议.也许可以回答另一个问题:是否有详尽的清单列出哪些特质类是C ++ 0x的新特性，哪些已经在C ++ 03中使用?也许有人知道链接到某个地方?

Update: The question what exactly makes a trait a trait seems a bit controversy in the details. Maybe a another question could be answered: Is there a comprehensive list which of the trait-like classes are new to C++0x, and which ones have already been in C++03? Maybe someone knows of a link to somewhere?

推荐答案

• * numeric_limits *绝对表示数字类型的一组特征.
• 所有要求，例如"CopyAssignable"等，实际上都是特征，请参见关于特征的这篇论文

  对于其他人，我不能发表评论，但有疑问时:

  For the others I cannot comment but when in doubt:

  将特征视为一个小物体，其主要目的是携带另一个对象或算法用来确定策略"的信息或实施细节".-Bjarne Stroustrup

  Think of a trait as a small object whose main purpose is to carry information used by another object or algorithm to determine "policy" or "implementation details". - Bjarne Stroustrup

  更新:仅对霍华德提供的广泛清单做出一小部分贡献:

  Update: to just make my small contribution to the extensive list Howard provided:

  我误以为TR1的 type特质和 regex特质属于技术上不是C ++ 0x中新特性束的一部分(即使新的即将发布的标准已大大扩展了类型特征).请参阅霍华德对此的评论和澄清.

  I was wrongly under the impression that the type traits and regex traits beeing part of the TR1 are technically not part of the new traits bunch in C++0x(even though the type traits have been greatly extended by the new upcoming standard). See Howard's comment and clarification about that.

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