I first heard of the concept of succinct data structures from Edward Kmett, a famous Haskeller behind many popular Haskell libraries. He gave a talk on succinct data structures a long time ago: http://youtu.be/uA0Z7_4J7u8
There is also HaskellWorks packages like https://hackage.haskell.org/package/hw-xml
Thank you for sharing this link!