Brian Boutel wrote
> Option 2 is closer to what the syntax of imports, read as English, suggests
> is intended, but, if it wasn't for that, I'd be promoting option 1.
> The primary purpose of being able to restrict imports is to avoid name
> clashes, and with qualified import there is no risk of a clash, so no need
> for restrictions.
This is not true since Haskell allows for the renaming of modules on
imports. If you look at the example in section 5.3.2 of the report,
there is the example
module M where
import qualified Foo as A
import qualified Bar as A
x = A.f
Obviously there is a name clash if both, Foo and Bar export symbol f.
> Even with option 2, there is scope for confusion. "Import" without
> "qualified", imports both qualified and unqualified names, but adding the
> word "qualified" doesn't make any difference to the position of qualified
> names, but instead silently fails to import unqualified names.
I don't understand what confusion you see here. What do you mean by the
"position of names"?
> There is still a strange asymmetry, too. Whereas adding "qualified" to
> "import Modname ( a, b, c)" doesn't change which entities are imported, just
> the ability to refer to them by unqualified names, adding qualified" to
> "import Modname hiding ( a, b, c)" has the effect of importing everything
> that was previously hidden.
I don't see that this applies to option 2. Maybe the formulation is
still not clear enough, but in my reading (and I think this is the
intended one) it says that the list of imported entities is the same
regardless of whether you use qualified on the import or not. The
qualified keyword only prevents the use of unqualified references to
these entities. So if in your example the module Modname exports
entities a, b, c, d, and e, then after import Modname hiding (a,b,c)
only d and e are imported and then same is true for import qualified
Modname hiding (a,b,c)
> Simon Peyton-Jones wrote:
> [...]
> > There are two consistent positions
> >
> > 1. Every import of module A (no matter how constrained) imports
> > all of A's exports with qualified names. Import of qualified names is
> > unaffected by both hiding clauses and the explicit entity list
> >
> > 2. The explicit entity list, or hiding clause, for an import determines
> > which
> > entities are imported. The qualified names of all these entities are
> > brought
> > into scope; in addition, for an unqualified import the unqualified names
> > are
> > brought into scope too.
Regards
Wolfgang
--
Wolfgang Lux Phone: +49-251-83-38263
Institut fuer Wirtschaftinformatik FAX: +49-251-83-38259
Universitaet Muenster Email: [EMAIL PROTECTED]
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