declaration of an incomplete private type before the private part
in [ADA]
|
Prev: Problem with Jewl on GPS and AdaGide
Next: declaration of an incomplete private type before the privatepart
From: Javi on 1 Feb 2008 03:28 hi guys, I'm very newbye to ADA, so my apologizes in advance. My problem: I need to do a declaration such as: ----------------------------------------- .... type ListNode is private; type List is private; package IterList is new Iterators (Creator => List, Item => ListNode, getFirst => Lists.getFirst, getNext => Lists.getNext, isLast => Lists.isLast); function makeIter (L : List) return IterList.Iterator; .... private: (complete declaration of ListNode and List) ----------------------------------------- The problem is that I need to complete the type (ListNode and List) before instancing the new package. But I do not know how to do that! The only solution I have found is to declare the types non-private and then give them the complete declaration. Obviously, this solution does not satisfy me since I want to make the types private. Can anyone help me, please? Thanks in advance, Javier
From: Javi on 1 Feb 2008 04:53 On 1 feb, 09:49, Niklas Holsti <niklas.hol...(a)tidorum.invalid> wrote: > Javi wrote: > > My problem: I need to do a declaration such as: > > > ----------------------------------------- > > ... > > type ListNode is private; > > type List is private; > > > package IterList is new Iterators (Creator => List, > > Item => ListNode, > > getFirst => Lists.getFirst, > > getNext => Lists.getNext, > > isLast => Lists.isLast); > > > function makeIter (L : List) return IterList.Iterator; > > ... > > private: > > (complete declaration of ListNode and List) > > ----------------------------------------- > > > The problem is that I need to complete the type (ListNode and List) > > before instancing the new package. But I do not know how to do that! > > The only solution I have found is to declare the types non-private and > > then give them the complete declaration. Obviously, this solution does > > not satisfy me since I want to make the types private. > > As I understand it, you want to instantiate the Iterators package > before the "private" part, because you want to use the type > Iterator, defined in the instance, in the declaration of public > oeprations (makeIter). One way to work around this problem is to > define a new type for that purpose: > > type ListNode is private; > type List is private; > type ListIterator is private; -- Added. > > function makeIter (L : List) return ListIterator; > > private > > type ListNode is ... -- Complete declaration. > type List is ... -- Complete declaration. > > packate IterList is new Iterators (....); -- As above. > > type ListIterator is new IterList.Iterator; > > HTH, > > -- > Niklas Holsti > Tidorum Ltd > niklas holsti tidorum fi > . @ . many thanks :-)
From: Robert A Duff on 1 Feb 2008 09:00
Javi <fjvera(a)gmail.com> writes: > hi guys, > > I'm very newbye to ADA, so my apologizes in advance. > > My problem: I need to do a declaration such as: > > ----------------------------------------- > ... > type ListNode is private; > type List is private; > > package IterList is new Iterators (Creator => List, > Item => ListNode, > getFirst => Lists.getFirst, > getNext => Lists.getNext, > isLast => Lists.isLast); > > function makeIter (L : List) return IterList.Iterator; > ... > private: > (complete declaration of ListNode and List) > ----------------------------------------- > > > The problem is that I need to complete the type (ListNode and List) > before instancing the new package. But I do not know how to do that! > The only solution I have found is to declare the types non-private and > then give them the complete declaration. Obviously, this solution does > not satisfy me since I want to make the types private. This is a flaw in the design of Ada. You can't instantiate a generic with a private type, in the same package where the private type is declared, and make the instantiation visible to clients (i.e. put it in the visible part). Your solution above (don't make it private) works. Niklas Holsti gave another solution. A third solution is to put the instantiation in a child package, or make it a child itself. Then clients have to "with" both the parent and the child. This won't work if the private part needs to see the instantiation, but it's OK if the body needs to see the instantiation. - Bob |