VHDL Issue Number:      2043

Language_Version:       VHDL-2002
Classification:         Language Definition Problem
Summary:                numeric VALUE attribute parameter can't have sign
Relevant_LRM_Sections:  14.1 Predefined attributes, 13.4 Abstract literals
    
Related_Issues: 
Key_Words_and_Phrases:  predefined attribute, value, abstract literal
Authors_Name:           James Unterburger
Authors_Phone_Number:   503.685.0860
Authors_Fax_Number:     503.685.0921
Authors_Email_Address:  jamesu@model.com
Authors_Affiliation:    Model Technology
Authors_Address1:       8005 SW Boeckman Road
Authors_Address2:       Wilsonville, OR 97070
Authors_Address3:   

Current Status:         Analyzed

Superseded By:

------------------------
Date Submitted:         15 October 2004
Date Analyzed:          5 May 2005
Author of Analysis:     Deepak Pant
Revision Number:        1
Date Last Revised:      15 October 2004

Description of Problem
----------------------
The Result description of predefined attribute T'VALUE(X) states
that the parameter X be the string representation of a value of type T
as defined in Clause 13.  A value of a numeric type, when it contains
an abstract literal (as it must for integer and floating point types
and optionally for physical types), must use the syntax given in
"13.4 Abstract literals", which does not allow a sign "+" or "-" to
be part of the literal.  This makes it impossible easily to represent
negative numeric values:  INTEGER'VALUE("-123") is illegal.

Proposed Resolution
-------------------
Allow an optional sign in the abstract literal portion of the string
representation of a value of a numeric type.  This was stipulated thus
in "14.3 Package TEXTIO" for the string representation of INTEGER and
REAL values.

VASG-ISAC Analysis & Rationale
------------------------------
This is a valid request. The definition of T'Value needs to be updated 
on the lines of section 14.3.


VASG-ISAC Recommendation for IEEE Std 1076-2002
-----------------------------------------------
None.

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

The wording for the definition of T'Value as defined in section 14.1 should 
be modified from

"If T is a numeric type or subtype, the parameter may be expressed either 
as a decimal literal or as a based literal."

to

"If T is a numeric type or subtype, the parameter may be expressed either 
as decimal literal or a based literal, with the addition of an optional 
leading sign. No spaces can occur between the sign and the remainder of 
the value."



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