The library (opencog/haskell) implements Haskell bindings. Right now, it is automatically installed, but if you want to reinstall, go to opencog/haskell and run:

stack build --extra-lib-dirs=/usr/local/lib/opencog

For appropiate Haddock documentation on the haskell library look at: opencog-atomspace

Dependencies:

haskell-atomspace library

The wiki page describes both how to run it and the core functions that are provided.