c++ lambdas how to capture variadic parameter pack from the upper scope

Question

I study the generic lambdas, and slightly modified the example, so my lambda should capture the upper lambda\'s variadic parameter pack. So basically what is given to upper

Answer 1

The perfect forwarding is another question, I'm curious is it possible here at all?

Well... it seems to me that the perfect forwarding is the question.

The capture of ts... works well and if you change, in the inner lambda,

printer(std::forward(ts)...);

with

printer(ts...);

the program compile.

The problem is that capturing ts... by value (using [=]) they become const values and printer() (that is a lambda that receive auto&&...vars) receive references (& or &&).

You can see the same problem with the following functions

void bar (int &&)
 { }

void foo (int const & i)
 { bar(std::forward(i)); }

From clang++ I get

tmp_003-14,gcc,clang.cpp:21:4: error: no matching function for call to 'bar'
 { bar(std::forward(i)); }
   ^~~
tmp_003-14,gcc,clang.cpp:17:6: note: candidate function not viable: 1st argument
      ('const int') would lose const qualifier
void bar (int &&)
     ^

Another way to solve your problem is capture the ts... as references (so [&]) instead as values.