Returning Lambdas from Functions

Yes, you can return a lambda from a function. However, specifying the return type can be a bit tricky.

One way to do this is to use auto as the return type and let the compiler deduce it:

1#include <iostream>
2
3auto MakeLambda() {
4  return [] {
5    std::cout << "Hello from Lambda!\n";
6  };  
7}
8
9int main() {
10  auto MyLambda{MakeLambda()};
11  MyLambda();
12}

1Hello from Lambda!

However, if you need to explicitly specify the return type (for example, if you're implementing a function declared elsewhere), you can use std::function from the <functional> header:

1#include <functional>
2#include <iostream>
3
4std::function<void()> MakeLambda() {
5  return [] {
6    std::cout << "Hello from Lambda!\n";
7  };
8}

Here, std::function<void()> specifies that the function returns a callable that takes no arguments and returns void.

You can adjust the template arguments to match the parameters and return type of your lambda. For example, std::function<int(std::string)> would be a callable that accepts a std::string and returns an int.