Re: A question about syntax or semantics

[Brad Moore <brad.moore@shaw.ca>]

On 14-05-17 04:56 PM, Victor Porton wrote:
>  From Ada2012 Reference Manual:
>
> arm2012.html/rm-4-1-3.html
>
> [[[
> A selected_component that is not an expanded name shall resolve to denote
> one of the following:
>
>      A view of a subprogram whose first formal parameter is of a tagged type
> or is an access parameter whose designated type is tagged:
> ]]]
>
> Why it is significant to have it only for the first formal parameter?
>
> Please explain with examples.
>
>

This question is worded like an exam question, so rather than give the 
answer directly, I'll respond with another question that might shed some 
light on your question.

with Ada.Containers.Doubly_Linked_Lists;

procedure X is
    package Integer_Lists is new
        Ada.Containers.Doubly_Linked_Lists (Element_Type => Integer);
     List1, List2 : Integer_Lists.List;
begin
    List1.Append(1);
    List2.Append(2);

    List1.Move(List2);
end;

If we didn't have the rule that you are asking about, what could we say 
about the Move call in the example above? Which list is the Source, and 
which list is the Target parameter? Is List1 getting moved into List2, 
or is it the other way around?

Brad