lambda函数可以模板化吗？ [英] Can lambda functions be templated?

问题描述

在C ++ 11中，有一种方法来模板lambda函数吗？

In C++11, is there a way to template a lambda function? Or is it inherently too specific to be templated?

我理解我可以定义一个典型的模板类/函数，但问题更像是：语言允许模板lambda函数？

I understand that I can define a classic templated class/functor instead, but the question is more like: does the language allow templating lambda functions?

推荐答案

UPDATE 2014：C ++ 14今年已经发布，现在提供多态lambdas相同的语法比本例中。一些主要的编译器已经实现了它。

UPDATE 2014: C++14 have been released this year and now provide Polymorphic lambdas with the same syntax than in this example. Some major compilers already implements it.

在C ++ 11中，可悲的是没有。多态性lambdas在灵活性和力量方面将是非常好的。

At it stands (in C++11), sadly no. Polymorphic lambdas would be excellent in terms of flexibility and power.

他们最终成为单态的原因是因为概念。概念使得这种代码情况困难：

The original reason they ended up being monomorphic was because of concepts. Concepts made this code situation difficult:

template <Constraint T>
void foo(T x)
{
    auto bar = [](auto x){}; // imaginary syntax
}

在约束模板中，您只能调用其他约束模板。 （否则不能检查约束。）可以 foo invoke bar（x）？

In a constrained template you can only call other constrained templates. (Otherwise the constraints couldn't be checked.) Can foo invoke bar(x)? What constraints does the lambda have (the parameter for it is just a template, after all)?

概念还没有准备好处理这种事情;它需要更多的东西，如 late_check （其中的概念没有选中，直到调用）和东西。更简单的只是放弃所有的并坚持单态lambdas。

Concepts weren't ready to tackle this sort of thing; it'd require more stuff like late_check (where the concept wasn't checked until invoked) and stuff. Simpler was just to drop it all and stick to monomorphic lambdas.

然而，随着从C ++ 0x删除概念，多态lambdas成为一个简单的命题。但是，我找不到任何建议。 ：（

However, with the removal of concepts from C++0x, polymorphic lambdas become a simple proposition again. However, I can't find any proposals for it. :(

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