使用自由函数作为伪构造函数来利用模板参数推导 [英] Using free function as pseudo-constructors to exploit template parameter deduction

问题描述

是否使用自由函数作为伪构造函数来避免显式指定模板参数是一种常见模式/惯用法？

Is it a common pattern/idiom to use free functions as pseudo-constructors to avoid having to explicitly specify template parameters?

例如，每个人都知道 std :: make_pair ，它使用其参数来推导对类型：

For example, everyone knows about std::make_pair, which uses its parameters to deduce the pair types:

template <class A, class B>
std::pair<A, B> make_pair(A a, B b)
{
  return std::pair<A, B>(a, b);
}

// This allows you to call make_pair(1, 2),
// instead of having to type pair<int, int>(1, 2)
// as you can't get type deduction from the constructor.

STL还在< functional> code>（ bind1st ， not1 ， ptr_fun ，etc ...）

The STL also makes heavy use of this in <functional> (bind1st, not1, ptr_fun, etc...)

我发现自己经常使用，所以我只是想知道是否有很多其他人使用它，如果有一个名称为这种模式？

I find myself using this quite often, so I was just wondering if many other people use it, and if there is a name for this pattern?

推荐答案

显然它被称为对象生成器。请参见更多C ++成语和Boost。

Apparently it's called "Object Generator". See "More C++ Idioms" and "Boost" on this topic.

我个人认为它非常有用，它使用它。

I personally find it very useful and use it alot.

此外，我认为可能会看到表达式模板作为对象生成器的一种特殊形式，因为它们都是通过操作数类型和数据来构造复杂类型也手动指定。

Also, I think one might see expression templates as a special form of object generators, since all they do is construct complex types by means of operand types and data you normally could specify also manually. Except, they are calling the generators implicitly

a + b + c =>
  Add<Add<A, B>, C>(...)

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