[Haskell] ANNOUNCE: ghc-vis

Dennis Felsing dennis at felsin9.de
Sat Sep 1 09:27:06 CEST 2012


I'm pleased to announce the relase of ghc-vis. This package provides a
way to visualize live data structures in GHCi, similar to GHCi's :print
and vacuum-cairo. Evaluation is not forced and you can interact with the
visualized data structures. This allows seeing Haskell's lazy evaluation
and sharing in action. Hopefully it will be useful for teaching Haskell
and understanding and debugging data structures.

Currently there's a linear view and a graph view using GraphViz. If you
want to see some examples of how it looks head to


or just give it a try like this:

$ cabal install ghc-vis
$ echo ":script $HOME/.cabal/share/ghc-vis-0.2.1/ghci" >> ~/.ghci
$ ghci
GHCi, version 7.4.2: http://www.haskell.org/ghc/  :? for help
λ> :vis
λ> let a = [1..3]
λ> :view a
λ> let b = cycle a
λ> :view b
λ> :view "foo" ++ "bar"
λ> :eval t1
λ> :switch

On Hackage: http://hackage.haskell.org/package/ghc-vis

I'm happy to hear about bugs, feature requests and other thoughts.


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