Heinrich Apfelmus wrote:
Lennart Augustsson wrote:
It's not often that one gets the chance to change something as fundamental as the scoping rules of a language. Nevertheless, I would like to propose a change to Haskell's scoping rules.
The change is quite simple. As it is, top level entities in a module are in the same scope as all imported entities. I suggest that this is changed to that the entities from the module are in an inner scope and do not clash with imported identifiers.
Why? Consider the following snippet
module M where import I foo = True
I like it.
That said, how does the the fact that the scope is nested affect the export list? If the module scope is inside the scope of the imports, then this means the name I.foo should appear in the export list, not foo , because the latter is in the outermost scope.
I think the solution to these problems is to rearrange the import declarations so that the syntax mirrors the scoping rules. In other words, I boldly propose to move the import declaration *before* the module declaration, i.e.
import I module M where foo = True
or even
import I where module M where foo = True
This way, it is clear that the module M opens an inner scope and that the export list of M uses the names from the inner scope.
Actually, the latter syntax should be import I in ... let import I in ... The idea is that this mirrors a let expression. (The "where" keyword would be misleading.) Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com