VHDL Issue Number:      0166
Classification:         Language Deficiencies and Modeling Problems
Language Version:       VHDL-87
Summary:                Enumeration literal to string conversion needed.
Related Issues:         None.
Relevant LRM Sections:  14.1
Key Words and Phrases:  Enumeration literal, predefined attributes
Current Status:         Submitted
1076-1993 Disposition:  Closed (All Issues Completely Addressed)
Disposition Rationale:  LRM addresses these concerns now.
Superseded By:          N/A
-----------------------
Date Submitted:         1991/03/14
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: 1995/05/13 19:34:42 $


Description of Problem
----------------------
There is currently no convenient way to convert enumeration literals to
strings.  Such a facility is useful, e.g., in assertion statements and can also
simplify the use of TextIO.


Proposed Resolution
-------------------
Copying Ada, define the following three additional predefined attributes (see
Ada Section 3.5.5 for the Ada versions of these predefined attributes):

        T'WIDTH
                Kind:           Value
                Prefix:         Any discrete or physical type or subtype T.
                Result type:    *universal_integer*.
                Result:         The maximum image length of all over all values
                                of the subtype T.  (The *image* is the sequence
                                of characters returned by the attribute IMAGE,
                                see below.)  If T is a null range, the result
                                is zero.

        T'IMAGE(X)
                Kind:           Function
                Prefix:         Any discrete or physical type or subtype T.
                Parameter:      An expression whose type is the base type of T.
                Result type:    Type String.
                Result:         The *image* of the value of X; that is, a
                                sequence of characters representing the value
                                in display form.  The image of an integer value
                                is the corresponding decimal literal without
                                underlines, leading zeros, exponent, or
                                trailing spaces, but with a single leading
                                character that is either a minus sign or a
                                space.  The index range of the result is an
                                ascending range whose lower bound is one and
                                whose upper bound is the length of the string.

                                The image of an enumeration value is either the
                                corresponding identifier in upper case or the
                                corresponding character literal (including the
                                two apostrophes); neither leading nor trailing
                                spaces are included.

                                The image of a value of a physical type is the
                                image of position number of the physical value
                                followed by a single space followed by the
                                image of the base unit in upper case.

        T'VALUE (X)
                Kind:           Function
                Prefix:         Any discrete or physical type or subtype T.
                Parameter:      An expression whose type is type String.
                Result type:    The base type of T.
                Result:         The value of type or subtype T whose image is
                                the parameter, stripped of extraneous
                                whitespace and converted to upper case.
                Restrictions:   An error occurs if there is no value of type or
                                subtype T whose image is the parameter (after
                                stripping and case shifting, if required).

(Note, there has been submitted a European requirement that covers 'IMAGE and
'VALUE; this one is provided to add 'WIDTH and to suggest LRM language.)


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


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


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