VHDL Issue Number:      1038
Classification:         Language Definition Problem
Language Version:       VHDL-93
Summary:                The definitions of A'LEFT, A'RIGHT, A'HIGH, A'LOW,
                        A'RANGE, and A'REVERSE_RANGE are ill-defined when
                        the value of the parameter is 0 or negative
Related Issues:         0202
Relevant LRM Sections:  14.1
Key Words and Phrases:  'LEFT, 'RIGHT, 'HIGH, 'LOW, 'RANGE, 'REVERSE_RANGE,
                        predefined attributes
Current Status:         Submitted
1076-1993 Disposition:  N/A
Disposition Rationale:  N/A
Superseded By:          N/A
-----------------------
Date Submitted:         1991/03/16
Author of Submission:   Paul Menchini (edited by Bill Paulsen)
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:    N/A
Author's Net Address:   mench@clsi.com
----------------------
Date Analyzed:          TBD
Author of Analysis:     TBD
Revision Number:        $Revision: 1.6 $
Date Last Revised:      $Date: 1995/05/15 21:26:37 $


Description of Problem
----------------------
(This IR supersedes IR 0202.)

The description of the parameter for A'LEFT, A'RIGHT, A'HIGH, A'LOW,
A'RANGE, and A'REVERSE_RANGE all state:

  "A locally static expression of type universal_integer, the value of
  which must not exceed the dimensionality of A.  If omitted, it defaults
  to 1."

Such language does not preclude attributes such as A'LEFT(0), which is
nonsensical.


Proposed Resolution
-------------------
Change the parameter descriptions for A'LEFT, A'RIGHT, A'HIGH, A'LOW,
A'RANGE, and A'REVERSE_RANGE to permit positive values only.


VASG-ISAC Analysis & Rationale
------------------------------
This appears to be an oversight in the LRM.


VASG-ISAC Recommendation for IEEE Std 1076-1993
-----------------------------------------------
Change the parameter descriptions for A'LEFT, A'RIGHT, A'HIGH, A'LOW,
A'RANGE, and A'REVERSE_RANGE to:

  "A locally static expression of type universal_integer, the value of
  which must must be positive and must not exceed the dimensionality of A.
  If omitted, it defaults to 1."


VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
Add the above language to the LRM.