cast list to list where B inherits A

Answer 1

Your intuition (and juanchopanza's comment) is correct - the lists are completely unrelated types.

The options are:

1. use list everywhere in the first place, even when you know the dynamic type is B* or C*
2. write a wrapper over list which casts to/from the correct dynamic type - this is equivalent to the (un)boxing behaviour in Java generics

3. re-write doSomething as a function template whose only constraint is that the types be convertible

   template 
   void doSomething(Sequence1 &x, Sequence2 &y) {
     // require only that *x.begin() is convertible with *y.begin(), etc.
   }
   

   I'd also agree with Kerrek's suggestion that this should use iterators instead, but that doesn't change the type requirement significantly - you just get two iterator type params instead of two container type params