Another question wrt hiding imports

Wolfgang Lux [email protected]
Thu, 12 Jul 2001 15:26:08 +0200


After the recent discussion import hiding clauses in import =

declarations, I was wondering what the meaning of hiding clauses is in =

the case of algebraic data types (or classes).

For instance if a have

  module A where
    data T =3D A | B

which entities are imported when I include the declaration

  import A hiding(T)

in a module? The report is not clear about this but I would expect that =

this imports data constructors A and B into the current module but not =

the type constructor T -- otherwise, what would be the meaning of =

import A hiding(T(B))?

However, if this is true it is possible to export data constructors =

without their type via

  module B(module A) where
    import A hiding(T)

which contradicts the statement in section 5.2 on p.64, that the form =

module m is equivalent to listing all entities imported from that =

module, because I cannot list a data constructor (without its type) in an=
 =

export specification.

Wolfgang


--
Wolfgang Lux				  Phone: +49-251-83-38263
Institut fuer Wirtschaftinformatik	    FAX: +49-251-83-38259
Universitaet Muenster		      Email: [email protected]