A few questions

[Laurent <daemon2@internet.lu>]

Hi

1) Trying to implement a search function in my linked list. Doesn't compile because the return type :List_Ptr is not visible in the ads file?

spec:

   function Search (L : in List; Element : in Element_Type) return List_Ptr;
   -- Pre: L is defined; L may be empty; Element is a scalar type
   -- Post: returns access to found node

body

   function Search (L : in List; Element : in Element_Type) return List_Ptr is
      Temp : List_Ptr;
      Current : List;

   begin
      Current := L.Head;
      while Current.Head /= null loop
         if Equals(Current.Head.Element, Element) then
            Temp:= Current.Head;
            return Temp;
         end if;
         Current.Head := Current.Head.Next;
      end loop;
   end Search;

The List_Ptr is defined as:

private

   ----------
   -- List --
   ----------

   type List_Node;
   type List_Ptr is access List_Node;
   type List_Node is record
      Element : Element_Type;
      Next    : List_Ptr;
      Previous:List_Ptr;
   end record;

   type List is record
      Head : List_Ptr;
      Tail : List_Ptr;
   end record;

I have put the search function in a child package.

2) Tried the same thing but this time using an iterator but fails with 

        65:20 (Ada 2005) cannot copy object of a limited type (RM-2005 6.5(5.5/2))
        65:20 return by reference not permitted in Ada 2005
on 

return It;

spec

   function Search (L : access List; Element : Element_Type) return Iterator;
   -- Pre: L is defined; L may be empty; Element is a scalar type
   -- Post: returns access to found node

body

   function Search (L : access List; Element : Element_Type) return  Iterator is
      It : Iterator (L);

   begin
      Start (It);
      while not Done (It) loop
         if Equals (It.This.Element, Element) then
            return It;
         end if;
         Next(It);
      end loop;
   end Search;

The Iterator is defined as:

private

   --------------
   -- Iterator --
   --------------

   type Iterator (L : access List) is limited
      record
         This :  List_Ptr;
      end record;

I have tried to understand RM-2005 6.5(5.5/2) but don't know what 

"If the result subtype of the function is defined by a subtype_mark, the return_subtype_indication shall be a subtype_indication. The type of the subtype_indication shall be the result type of the function"

is supposed to look like. 

If someone could enlighten me on both problems.

https://github.com/Chutulu/Chapter-15.git

3) How can I take a look at the assembler code of both versions? Just curious to see if there is actually a difference between both versions. I have no idea of assembler but that doesn't keep me from trying.

Thanks

Laurent