[Haskell-beginners] Error while using indices and elem

[Dan Serban]

Hello Nishant,

It's not clear whether you're implementing graph functionality as a
device for learning Haskell, or whether you need it as a kind of a
library to support future programs.

If it's the latter, I want to point you to the Data.Graph module in
the containers package:
http://hackage.haskell.org/package/containers-0.2.0.1/docs/Data-Graph.html