Using auto in a lambda function

Question

#include 
#include 

void foo( int )
{
}

int main()
{
  std::vector< int > v( { 1,2,3 } );

  std::for_each( v.begin(), v.end()         


        

Answer 1

This was discussed briefly by Herb Sutter during an interview. Your demand for auto arguments is in fact no different from demanding that any function should be declarable with auto, like this:

auto add(auto a, auto b) -> decltype(a + b) { return a + b; }

However, note that this isn't really a function at all, but rather it's a template function, akin to:

template 
auto add(S a, T b) -> decltype(a + b) { return a + b; }

So you are essentially asking for a facility to turn any function into a template by changing its arguments. Since templates are a very different sort of entity in the type system of C++ (think of all the special rules for templates, like two-phase look-up and deduction), this would be radical design change with unforeseeable ramifications, which certainly isn't going to be in the standard any time soon.