Re: why are these unknown identifiers?

[agate!spool.mu.edu!news.cs.indiana.edu!arizona.edu!east.pima.edu!rharwood]

In article <9109101616.aa26718@PARIS.ICS.UCI.EDU>, jduarte@liege.ICS.UCI.EDU
(Jose Duarte) writes:

> package X is
> 	type DIRECTIONS is (UP,DOWN,LEFT,RIGHT);
> end X;
> -----------------------------------------
> with X;
> package Y is
> 	subtype DIRECTIONS is X.DIRECTIONS;
> end Y;
> -----------------------------------------
> with TEXT_IO;
> use  TEXT_IO;
> with Y;
> procedure BUG is
>   V1 : Y.Directions := Y.UP;    -- Y.UP is unknown
>   V2 : Y.Directions := Y.DOWN;  -- Y.DOWN is unknown
> begin
>   null;
> end BUG;
> Can someone tell me why "Y.UP" and "Y.DOWN" are unknown identifiers
> within the procedure BUG? 

To answer your question, I propose that you temporarily change package Y to:
    with X;
    package Y is
 	type DIRECTIONS is new X.DIRECTIONS;
    end Y;
NOW you don't need X... the reason is that the IDENTIFIERS (for enumerated
types) and the OPERATORS (for virtually all non-private types) are considered
to be "declared" at the same scope of the TYPE declaration... and a subtype
does NOT declare a new type.  Therefore the SUBTYPE Y.DIRECTIONS is heavily
dependent on the declaration of X.DIRECTIONS... while a TYPE Y.DIRECTIONS
establishes the identifiers and operations inside the scope of Y.

I hope I've communicated this well.
Ray
-----
Ray Harwood           |Data Basix           |Associate Faculty,    
Voice: (602)721-1988  |PO Box 18324         |   Pima Community College
FAX:   (602)721-7240  |Tucson, AZ 85731     |Instructor in Ada and Pascal
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