VHDL Issue Number:      0208
Classification:         Language Definition Problem
Language Version:       VHDL-87
Summary:                The expression defining the value of a constant does
                        not have to be of the type of the constant.
Related Issues:         None.
Relevant LRM Sections:  4.3.1.1
Key Words and Phrases:  Constant declarations, type constraints
Current Status:         Submitted
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  Section 4.3.1.1 was updated.
Superseded By:          N/A
-----------------------
Date Submitted:         1991/03/18
Author of Submission:   Paul Menchini
Author's Affiliation:   CAD Language Systems, Inc.
Author's Post Address:  P.O. Box 13036
                        Research Triangle Park, NC  27709-3036
Author's Phone Number:  (919) 361-1913
Author's Fax Number:    
Author's Net Address:   mench@clsi.com
-----------------------
Date Analyzed:          TBD
Author of Analysis:     TBD
Revision Number:        $Revision: 1.9 $
Date Last Revised:      $Date: 1995/08/04 01:45:13 $


Description of Problem
----------------------
Paragraph 4 of Section 4.3.1.2 states (in part):

        If the signal declaration includes the assignment symbol
        followed by an expression, it must be of the same type as the
        signal.

Similarly, paragraph 2 of Section 4.3.1.3 states:

        If the variable declaration includes the assignment symbol
        followed by an expression, the expression specifies an initial
        value for the declared variable; the type of the expression must
        be that of the variable.

There is no analogous statement in Section 4.3.1.1; instead paragraph 2 of this
section merely states (in part):

        If the assignment symbol ":=" followed by an expression is
        present in a constant declaration, the expression specifies the
        value of the constant.

It seems that the lack of requirement that the type of the expression be that
of the constant is an oversight and not a deliberate omission.


Proposed Resolution
-------------------
Change the first sentence of paragraph 2 of Section 4.3.1.1 to read:

        If the assignment symbol ":=" followed by an expression is
        present in a constant declaration, the expression specifies the
        value of the constant; the type of the expression must be that
        of the constant.

Moreover, the "it" in the first sentence of paragraph 4 of Section 4.3.1.2 may
be ambiguous.  The first sentence might be clearer if expressed as:

        If the signal declaration includes the assignment symbol
        followed by an expression, the expression must be of the same
        type as the signal.


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


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


VASG-ISAC Recommendation for Future Revisions
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TBD