[Haskell-cafe] a poorly thought out suggestion for cabal and packages that have lots of instances

Stephen Tetley stephen.tetley at gmail.com
Tue Mar 16 09:03:04 EDT 2010

Hi Jeremy

Is this really a problem practically rather than hypothetically?

Data.Text and Syb-with-class - both are general, neither uses the
other for their implementation, adding a dependency to one sounds like
a bad idea - so making a separate 'instance' package seems most

Unless you believe otherwise, Data.Text appears more 'general' than
happstack-data, so Data.Text shouldn't provide happstack-data
instances. Then its a choice between adding a direct dependency on
Data.Text to happstack-data and defining the instance there or making
a separate instance package again.

A category on Hackage for 'instance' packages would seem to make sense
as would a naming convention for the packages, hopefully stopping any
proliferation of identical packages.

Best wishes


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