[Haskell] Re: Please check your dependencies on fgl

Christian Maeder Christian.Maeder at dfki.de
Tue Jun 8 05:39:23 EDT 2010

Ivan Lazar Miljenovic schrieb:
> We considered giving it a new name (fgl', etc.) but figured that in the
> long term this wouldn't be advantagous.  We feel that the situation is
> analogous to QuickCheck: when the new version came out most people kept
> using the old one until slowly the momentum shifted and more people
> started using the new version (without checking in depth, Roel's Hackage
> mirror reports QC-2.x now has 153 reverse dependencies as opposed to 127
> reverse dependencies for QC-1.y).
> If we changed the name, then the "emotional attachment" that the Haskell
> community has to FGL being the de-facto graph library means that people
> would keep using the old version.  Whilst we also face the possible
> problems of people not liking the old version and thus automatically
> dismissing the new version, I think this is a much more unlikely
> scenario.

I'm afraid you'll destroy the "emotational attachment" to fgl by
annoying incompatibilities (and possibly interfering new bugs).

Although parsec-3 can be used as an replacement for parsec-2 it would
have been better, they had different names (as argued elsewhere for the
haskell platform).

Changing a dependency in a cabal file is a small problem.
Those (unaware), who only mention "fgl", will fall over an
incompatibility (usually at installation time!) and simple say "fgl <
..." unless they are willing to change their code then.

Those who already have "fgl < ..." need to find an advertisement of a
"new and better fgl" anyway and can choose when to change their code.


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