VHDL Issue Number:      0234
Classification:         Editorial
Language Version:       VHDL-87
Summary:                Creation of type/subtype in integer type declaration.
Related Issues:         None
Relevant LRM Sections:  3.1.2
Key Words and Phrases:  integer type declaration, type, subtype
Current Status:         Submitted
1076-1993 Disposition:  Superseded (ISAC Issues Outstanding)
Disposition Rationale:  N/A
Superseded By:          1047
-----------------------
Date Submitted:         1991/03/08
Author of Submission:   Laurence Groves
Author's Affiliation:   Synopsys Inc.
Author's Post Address:  1098 Alta Ave.
                        Mountain View, CA 94043
Author's Phone Number:  (415) 962-5426
Author's Fax Number:    
Author's Net Address:   larry@Synopsys.COM
-----------------------
Date Analyzed:          TBD
Author of Analysis:     TBD
Revision Number:        $Revision: 1.9 $
Date Last Revised:      $Date: 1995/07/26 23:58:17 $


Description of Problem
----------------------
This issue is regarding a clarification.  There is some disagreement on
the interpretation of the following:

    1  entity E is
    2  end;
    3
    4  architecture A of E is
    5     type A is range 1 to 10;
    6     attribute Q : integer;
    7     attribute Q of A : type is 1;             -- not legal
    8     attribute Q of A : subtype is 1;          -- legal
    9  begin
   10  end A;

The disagreement is in the creation of a [anonymous] type and [named] subtype
in the type definition (line 5).

LRM 3.1.2 states:

        An integer type definition defines both a type and a subtype
        of that type.  The type is an anonymous type, the range of
        which is selected by the implementation; this range must be
        such that it wholly contains the range given in the integer
        type definition.  The subtype is a named subtype of this
        anonymous base type, where the name of the subtype is that
        given by the corresponding type declaration and the range
        of the subtype is the given range.

It is clear from the above LRM passage that the type mark that the name "A"
refers to (with an integer type definition) is a subtype, not a type (which is
unnamed).  When used in an attribute declaration (lines 7 and 8), the type mark
is "subtype."

Specifying the type mark as "type" is illegal.


Proposed Resolution
-------------------
Add the note after 3.1.2 stating that, if so desired, you need to attribute the
subtype and that it is illegal to attribute a type.


VASG-ISAC Analysis & Rationale
------------------------------
TBD


VASG-ISAC Recommendation for IEEE Std 1076-1987
-----------------------------------------------
TBD


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
TBD