Efficient queue in Haskell

Question

How can I efficiently implement a list data structure where I can have 2 views to the head and end of the list, that always point to a head a tail of a list without expensive ca

Answer 1

I'm not really a Haskell user, but I found a blog post which claims to describe a Haskell queue that can be operated on in amortized constant time. It's based on a design from Chris Okasaki's excellent Purely Functional Data Structures.