Re-export qualified?

Question

suppose you have two modules like

module Foo.A where  foo = 42 

and

module Foo.B where  foo = 12 

and you want to write a super module

module Foo (       module Foo.A     , module Foo.B     ) where  import Foo.A import Foo.B 

which re-exports those modules, you would get a name clash.

Is there a solution for this?

Answer 1

Basically, no. This has been a long-standing feature request by people like the authors of Gtk2hs. Gtk2hs has a very broad module hierarchy where it might make sense to both:

• Use the same name in several different modules (e.g. newButton in both Graphics.UI.Gtk.Buttons.Button and Graphics.UI.Gtk.Buttons.CheckButton)
• Provide the convenience to the user of importing all these modules with a single import statement

For now, if you want to reexport several modules together all you can do is:

• Avoid reusing names in the modules you wish to reexport
• Where appropriate, use type classes to allow the same name to be used for several different purposes

Answer 2

Good question. The Haskell Report addresses this:

Exports lists are cumulative: the set of entities exported by an export list is the union of the entities exported by the individual items of the list.

[...]

The unqualified names of the entities exported by a module must all be distinct (within their respective namespace).

According to my limited Haskell knowledge I'd say it's not possible.