Return one of two (or more) lambdas in C++

alexey_r_9204 0
Viewed 105

Since C++ lambdas have unique unnamed types, something like this doesn't work:

auto select_lambda() {
    if (someCondition())
        return []() { return 1; };
    else
        return []() { return 2; };
}

They can be wrapped into an std::function:

std::function<int()> select_lambda() { /* same body */ }

But this has a significant overhead. Is there a better way to achieve something similar? I had some preliminary ideas but none which I got working yet.

lambda c++
1 Answers

If your lambdas don't need to capture anything then you can prepend + to each of them to convert them to a regular function pointer:

auto select_lambda() {
    if (someCondition())
        return +[]() { return 1; };
    else
        return +[]() { return 2; };
}

If you need capturing lambdas then std::function would seem to be the best way to go.

user_57432880
Related