Using std::map where V has no usable default constructor

Question

I have a symbol table implemented as a std::map. For the value, there is no way to legitimately construct an instance of the value type via a default constructo

Answer 1

you could specialize std::map for your value-type. I'm not saying it's a good idea, but it can be done. I specialized scoped_ptr's dtor to fclose instead of delete.

Something like:

 template
 my_value_type& std::map::operator[](const K& k) 
 {
   //...
 }

This should allow you to insert the code you want into operator[] for your type. Unfortunately, I do not know of a way in current c++ to return only r values. In c++0x you might be able to use:

 template
 my_value_type&& std::map::operator[](const K& k) 
 {
   //...
 }

This will return an R-value reference (&&).