Hi Haskell-ers,<br>So I think I understand the idea of creating a heterogenous list using typeclasses and existentials, but I don't see how to filter the list<br>to retrieve elements of the list that are of only one type.<br>
<br>More concretely, taking the example <a href="http://haskell.org/haskellwiki/Existential_type">here</a> how could we take a list of shapes [Shape] and pull out all objects that are Squares?<br>I don't see an obvious way this makes sense.
<br>Is there a way of doing heterogenous lists that would make this possible?<br>