Re: Proposal: improve the Data.Tree API

-----Original message----- From: Henning Thielemann Sent: 14 Mar 2014, 09:39

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The idea was to provide two modules, Data.Tree and Data.Tree.Forest. The methods for Forest would be in Data.Tree.Forest. To use the modules, the users would write import qualified Data.Tree as Tree import qualified Data.Tree.Forest as Forest and then use the methods as Tree.lookupTree Tree.filter and Forest.filter

I find this naming scheme attractive. In order to break module cycles I usually define private modules. E.g.

Data.Tree.Private exports Tree, but the module is hidden Data.Tree.Forest imports Tree, exports Forest, module is exposed Data.Tree imports Tree and Forest, exports Tree, module is exposed

You are right, no dependency cycle here. Nevertheless, we probably have to export both Tree a and Forest a from Data.Tree, as the Tree datatype uses Forest. Forest is actually only type Forest a = [Tree a] so it is not such a big issue :) We should probably reexport Tree a and Forest a from Data.Tree.Forest too, so that users can use only Data.Tree.Forest module without Data.Tree. Cheers, Milan