new tutorial on acid-state, ixset, and lenses

Hello,

I just uploaded a new tutorial which covers three distinct, but related topics:

• acid-state - a native Haskell, noSQL, RAM-cloud database
• IxSet  - a multi-indexed collection type (similar to Data.Map but with support for  multiple keys)
• data-lens - a library which provides syntax that makes it easier to update nested records and other data types

The tutorial is available here:

http://happstack.com/docs/crashcourse/AcidState.html

The section on lenses is a great applied introduction to the concept which requires no understanding of Happstack, acid-state, or IxSet. So, even if you don't care about acid-state, you may find it useful if you have ever wondered what the heck lenses are.