How to invoke a lambda template?

Question

I was able to compile the following code with gcc:

template<typename... Pack>
auto func(Pack... x) {
    return (x + ...) ;
}

template<typename... Pack>
auto lamd = [](Pack... x) {
    return (x + ...) ;
};

I can invoke the function template with func(1,2,3), but I get an error when invoking a the lambda, with lamd(1,2,3) or lamd<int>(1,2,3).

Answer 1

For lambdas, you can make it generic lambda with the usage of auto.

auto lamd = [](auto... x) {
    return (x + ...) ;
};

Since C++20 you can uses an explicit template parameter list, but note that the template parameter list is still used with the operator() of the lambda, just as the usage of auto parameters. e.g.

auto lamd = []<typename... Pack>(Pack... x) {
    return (x + ...) ;
};

and then you can call it as lamd(1,2,3).

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