Johannes Waldmann
Sounds like the perfect example to illustrate the point that information shouldn't be doubled in the first place.
Yes, I suppose one could argue that.
Can you say why you want the type in the export list?
As a compact description of the module interface. Many people already do it, except that the signature is in a comment, and therefore not checked.
Or really, why you want an export list at all?
An explicit interface would be useful for many purposes besides machine-checked documentation. For instance, it could be used to eliminate the hs-boot or hi-boot files used by some compilers when dealing with recursive modules.
Presumably because it constitutes the module's "interface", but it is an ad-hoc thing (one interface per module). We already have the concept of "type class" which gives us re-usable interfaces. Isn't that much better?
The near correspondence between type classes, modules, and records, is well-known, yet still they are separate concepts in Haskell. Perhaps one day they will be merged. However, in the meantime, for both records and classes one is forced to give a signature to the contained elements/methods. For consistency, modules should do the same... Regards, Malcolm