Ada: Accessing individual elements of a generic list - list

Question

I've programmed a stack of generic numbers in Ada using a 'Indefinite_Doubly_Linked_Lists' list.
Pop & push operations are implemented with append and delete_last but for a sorting method I would need to access individual items of the list.
I did work out a sorting method using only append/prepend delete_last/first but the result is far from elegant (and maybe not correct)
procedure sort is
elem1: Item;
elem2: Item;
--l is a package-private Indefinite_Doubly_linked_lists'
begin
if Integer(MyList.Length(l)) > 1 then
for i in 0 .. Integer(MyList.Length(l))-1 loop
for j in 0 .. Integer(MyList.Length(l))-1 loop
--Inner sort loop
elem1 := MyList.Element(l.first);
l.Delete_First;
elem2 := MyList.Element(l.first);
l.Delete_First;
if elem1>elem2 then
l.Prepend(elem1);
l.Append(elem2);
else
l.Prepend(elem2);
l.Append(elem1);
end if;
end loop;
end loop;
end if;
end;
How do can I access individual elements (or iterate over) from a list of generic type?

Answer 1

A couple things:
Unless the point of your exercise is writing a sort, you could just...uh...use the generic sort:
package List_Sort is new MyList.Generic_Sorting;
If you're using an Ada 2012 compiler, generalized looping gives you easy access to each element:
procedure Iterate is
begin
for Elem of L loop
Put_Line(Item'Image(Elem));
end loop;
end Iterate;
If you're not using Ada 2012, you can make due with cursors, either on their own:
procedure Cursor_Iterate is
C : MyList.Cursor := L.First;
use type MyList.Cursor;
begin
loop
exit when C = MyList.No_Element;
Put_Line(Item'Image(MyList.Element(C)));
MyList.Next(C);
end loop;
end Cursor_Iterate;
or with MyList's Iterate procedure:
procedure Iterate
(Container : in List;
Process : not null access procedure (Position : in Cursor));