dig1 on Curious C++ Lambda Examples: Recursion, constexpr, Containers C++23 included

Comment on Curious C++ Lambda Examples: Recursion, constexpr, Containers C++23 included

Instead of using "this auto&&" trick to get recursive lambdas, I wonder why they didn't go with named lambdas (Clojure made it really nice). E.g.

    auto factorial23 = [] fact_recur (int n) {
        if (n <= 1)
            return 1;
        return n * fact_recur(n - 1);
    };

Maybe this has to do with the usual C++ complicated parsing rules... But, on the other hand, named lambdas, besides recursion, in the language mentioned above helps with stacktraces, so you get the idea where the issue could be, instead of getting an anonymous mangled name mess.

gpderetta 4y

Honestly approximately nobody cares about recursive lambdas in c++, it is mostly a party trick. The this auto syntax is just a side effect of the new 'explicit this' syntax that affects all member functions.

einpoklum 4y

Because `this auto&&` was not introduced to allow for recursive lambads. That's just a happy (though not very interesting) side effect. It was introduced so that you don't have to write duplicated code such as:

    class Awesome {
        // ...
        foo& my_method() { /* ... */ }    
        const foo& my_method() const { /* ... */ }
    };

and the extra duplication for lvalues and rvalues.

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