gcc has had those (as a non-standard C extension) for a while. Too bad it never made it into the standard.

https://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html#Nes...

Too bad it would be really nice for sort() etc.

Why would it make a difference? You can pass an anonymous function with two auto arguments as the comparison to sort.

It wouldn't pollute the file scope namespace. You can define it in eye sight of the sort call, steal variables from the nesting functions stack etc.

... but how's that different of what we have today ?

    std::sort(vec.begin(), vec.end(), 
              [] (const auto& lhs, const auto& rhs) { 
      return lhs.whatever < rhs.whatever;
    });

or

    auto sort_by_whatever = [] (const auto& lhs, const auto& rhs) { 
      return lhs.whatever < rhs.whatever;
    };
    std::sort(vec.begin(), vec.end(), sort_by_whatever);

Sorry was refering to C in that comment with no lambdas, with the GCC extension.