C ++ 14使用capture-specifier在lambda函数内增加一个值

Question

My task is to write a lambda function which increment a value, but I have to use value = 0 capture-specifier. I'm thinking about the following function:

auto lambda = [value = 0]{return ++value}

When this function is called it has to give an incremented value every time. But I know this implementation is wrong, because it's passed by value. How can I do this in C++14?

Answer 1

你需要使lambda变为可变：

auto lambda = [value = 0]() mutable {return ++value;};

Answer 2

You don't need a capture:

[]{ static int i=0; return ++i; }

Is all you need.