Currently, Haskell lacks production-grade bindings for mutable data structures, and has to rely on immutable data structures for storage.
For example, a sparse mutable array may be emulated by (IORef IntMap), and a mutable set may be emulated by (IORef Set). However, these data structures have to be reconstructed almost from scratch for each insertion/deletions, resulting in low performance.
The Pugs project implements Perl 6 on top of Haskell; we would need fast implementations for mutable sparse array, mutable ordered mappings, mutable resizable byte-buffers, as well as mutable string-indexed Hash tables.
One approach is to write a binding to Judy (judy.sf.net) or other C-based libraries, and present an API conformant to the existing Haskell libraries (e.g. MArray).
The result of this effort will be reusable to other Haskell projects as well.
Interested Mentors
Interested Students