VHDL Issue Number:      1066
Classification:         Language Definition Problem
Language Version:       VHDL-93
Summary:                Conversion function definition assumes different types.
Related Issues:         0127
Relevant LRM Sections:  12.6.2
Key Words and Phrases:  Composite Types, Type Conversion Function, Association Elements
Current Status:         Submitted
1076-1993 Disposition:  N/A
Disposition Rationale:  N/A
Superseded By:          N/A
-----------------------
Date Submitted:         1988/06/21
Author of Submission:   Ken Scott (edited by Daniel Barclay)
Author's Affiliation:   Vantage Analysis Systems, Inc.
Author's Post Address:  42840 Christy St., Suite 201
                        Fremont, CA   94538
Author's Phone Number:  (415) 659-0901
Author's Fax Number:    
Author's Net Address:   N/A
-----------------------
Date Analyzed:          TBD
Author of Analysis:     TBD
Revision Number:        $Revision: 1.7 $
Date Last Revised:      $Date: 1995/05/15 21:26:37 $


Description of Problem
----------------------
In the second full paragraph of chapter 12.6.2 (starts with "If a signal of a 
given ..."), there is an error.
   
The first statement reads:
    "If a signal of a given composite type has a source that is of a 
     different type (and therefore a conversion function or type conversion
     appears in the corresponding association element), then each scalar 
     subelement of that signal is considered to be active if the source 
     itself is active."

The problem with this text is that it does not take care of the
strange but legal case where the user has inserted a "type conversion
function" whose parameter and return value are of the same type:
    function SIMPLE_TCF( SOURCE : TM ) return TM;
   
This function does not translate between types, but nonetheless
may translate the actual value of the source to something the user
wants.  The correct thing to do would be to consider each scalar
subelement of the formal or actual to be active whenever its
source is active.  This is not implied in the LRM.
   
There is a similiar statement that has the same error later on in
the same paragraph concerning "port of a given composite type".



Proposed Resolution
-------------------
The following modified paragraph will fix the problem:
    "If a signal of a given composite type has a source WHICH GETS TRANS-
     LATED BY A CONVERSION FUNCTION OR TYPE CONVERSION APPEARING IN A PORT 
     ASSOCIATION ELEMENT, then each scalar subelement is considered to be 
     active if the source itself is active.  Similiarly, if a port of a 
     given composite type is associated with a signal WHOSE VALUE GETS 
     TRANSLATED BY A CONVERSION FUNCTION OR TYPE CONVERSION APPEARING IN 
     THE CORRESPONDING PORT ASSOCIATION ELEMENT, then each scalar subelement 
     of that port is considered to be active if the actual signal itself is 
     active."

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


VASG-ISAC Recommendation for IEEE Std 1076-1993
-----------------------------------------------
TBD


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