RE: [vhdl-200x-ft] VHDL-2005 package changes for read and write

Folks,

Thanks to Dave and Jim for drafting the message. I concur with Jim's
modifications to Dave's original.

Cheers,

PA

--
Dr. Peter J. Ashenden                        peter@ashenden.com.au
Ashenden Designs Pty. Ltd.                   www.ashenden.com.au
PO Box 640                                   Ph:  +61 8 8339 7532
Stirling, SA 5152                            Fax: +61 8 8339 2616
Australia                                    Mobile: +61 414 70 9106
> -----Original Message-----
> From: owner-vhdl-200x-ft@eda.org 
> [mailto:owner-vhdl-200x-ft@eda.org] On Behalf Of Jim Lewis
> Sent: Friday, 19 November 2004 02:19
> To: David Bishop
> Cc: vhdl-200x-ft@eda.org
> Subject: Re: [vhdl-200x-ft] VHDL-2005 package changes for 
> read and write
> 
> 
> David,
> I think at the meeting there was also a significant concern 
> about the overloading in std_logic_1164 and numeric_std, we 
> would be breaking old code that also overloaded these procedures.
> 
> I added a few suggestions below.  I put -- in front of lines 
> that I replaced.
> 
> Regards,
> Jim
> 
> > (This is the draft of a note we plan to put on 
> "comp.lang.vhdl" please 
> > review)
> > 
> > In the next update to VHDL we are planning several changes and 
> > additions to the standard packages.
> > 
> -- > One of the things we are planning to do is to move all of
> -- > the "read" and "write" procedures to where they are defined.
> 
> For the current packages, std_logic_1164, numeric_std, and 
> numeric_bit we plan to include the "read" and "write" 
> procedures in the package.  This will also be done for any 
> new packages of types introduced in this revision. Note, read 
> and write procedures for standard types (bit, bit_vector, 
> integer, ...) will still be located in std.textio.
> 
> Std_logic_textio has been donated to the IEEE.  All the read 
> and write functions that are proposed for std_logic_1164 are 
> intended to be backward compatible with this 
> std_logic_textio. As a result, we will be including a blank 
> std_logic_textio so that references to std_logic_textio will 
> not cause issues.
> 
> 
> -- > We have been donated "std_logic_textio", and plan to move all
> -- > of the procedures from that package into "std_logic_1164".
> -- > We will also provide a blank "std_logic_textio" so that
> -- > the name space will be preserved.  "numeric_std" will
> -- > have "read" and "write" procedures added to it.
> 
> 
> 
> > This means that the following code:
> > 
> > library ieee;
> > use ieee.std_logic_1164.all;
> > use ieee.std_logic_textio.all;
> > entity
> > ....
> > architecture
> > ...
> > write (L, slv5);
> > 
> > will still work because it will now find the "write" procedure in 
> > "std_logic_1164".
> > 
> > HOWEVER, the following will no longer work:
> > 
> > ieee.std_logic_textio.write (L, slv5);
> 
> 
> It also means that if you have defined your own read and 
> write procedures for the types in std_logic_1164, 
> numeric_std, or numeric_bit that you will need to comment 
> these procedures out in the packages in which you have defined them.
> 
> Is this an issue for you and if so how big?  Are you willing
> to trade the modifications to your packages in exchange for 
> what we feel is a better package architecture for the future?
> 
> Alternately would it be better to keep the read and write for 
> std_logic_1164, numeric_std, and numeric_bit in separate 
> packages such as std_logic_textio, numeric_std_textio, and 
> numeric_bit_textio? Our concern with this approach for 
> printing is that you need
> twice the number of packages for printing.   Consider that we
> are also introducing packages for fixed point and floating 
> point in this revision and that they would need to be done in 
> a manner consistent with numeric_std and std_logic_1164.
> 
> 
> -- > Is this an issue for people?
> -- > If you have written your own "read" and "write" routines these
> -- > will now cause a conflict with the ones in "std_logic_1164".
> -- > Would keeping the packages seperate be better?
> -- >
> 
> For details of the change proposal see:
>     http://www.eda-twiki.org/vhdl-200x/vhdl-200x-ft
> -- > Please take a look at:
> -- > http://www.eda-twiki.org/vhdl-200x/vhdl-200x-ft
> 
> For proposed revisions to the package (and to try them out) see:
>    http://www.eda-twiki.org/vhdl-200x/vhdl-200x-ft/packages/files.html
>    Note any debug help with the new packages would be appreciated.
> 
> 
> -- > for the 2005 updates page and
> -- > http://www.eda-twiki.org/vhdl-200x/vhdl-200x-ft/packages/files.html
> -- > for a preliminary copy of the new packages.
> -- > (Yes, we can use help debugging this code if you are available)
>