C++11 将 `auto` Lambda 更改为不同的 Lambda? [英] C++11 Change `auto` Lambda to a different Lambda?

问题描述

假设我有以下包含 lambda 的变量:

Say I have the following variable containing a lambda:

auto a = [] { return true; };

我希望 a 稍后返回 false.我可以做一些类似的事情吗?

And I want a to return false later on. Could I do something along the lines of this?

a = [] { return false; };

此语法给了我以下错误:

This syntax gives me the following errors:

binary '=' : no operator found which takes a right-hand operand of type 
'main::<lambda_a7185966f92d197a64e4878ceff8af4a>' (or there is no acceptable conversion)

IntelliSense: no operator "=" matches these operands
        operand types are: lambda []bool ()->bool = lambda []bool ()->bool

有没有办法实现这样的目标?我想将 auto 变量更改为不同的 lambda.我是一个初学者，所以我可能缺少一些关于 auto 或 lambdas 的知识.谢谢.

Is there any way to achieve something like this? I would like to change the auto variable to a different lambda. I'm relitively a beginner so I may be missing some knowledge about auto or lambdas. Thanks.

推荐答案

每个 lambda 表达式都会创建一个新的唯一类型，因此您的第一个 lambda 表达式的类型与第二个的类型不同 (示例).此外，lambda 的复制赋值运算符被定义为已删除(example)，因此您双重无法做这个.对于类似的效果，您可以将 a 设为 std::function 对象，尽管这会降低性能

Every lambda expression creates a new unique type, so the type of your first lambda is different from the type of your second (example). Additionally the copy-assignment operator of a lambda is defined as deleted (example) so you're doubly-unable to do this. For a similar effect, you can have a be a std::function object though it'll cost you some performance

std::function<bool()> a = [] { return true; };
a = [] { return false; };

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