Re: [vhdl-200x-ft] Revised FT16: context declarations and clauses

Selon Peter Ashenden <peter@ashenden.com.au>:

> Folks,
>
> Attached is a revised version of FT16, context declarations and context
> clauses, addressing issues discussed in today's telecon:
[...]
My comments:

1) Note that to use IEEE_STD_CONTEXT, you have to write:
 library IEEE;
 context IEEE.IEEE_STD_CONTEXT;
Maybe we should go further with only:
 context IEEE.IEEE_STD_CONTEXT;

2) The 'context' reserved word can either start a context_declaration or
 a context_reference. This is not very good.
 Suggestion:
  use context xxx;
 or
  with context xxx;

3)
    context_reference ::=
         context selected_name { , selected_name } ;
Should be:
    context_reference ::=
         context name { , name } ;

ie, you should accept:
  library IEEE;
  use IEEE.all;
  context IEEE_STD_CONTEXT;

4) Use of STD.STANDARD.all should indeed be forced, otherwise very odd
  things have to be precised.

5) A major (?) problem with the context clauses, as they are written in
VHDL LRM is that you don't easily know which design units you are using.
Ie, if your methodology is not to use 'ieee.std_logic_arith' (for example),
then it is difficult to check your designs do not use it.
Ada has 'with clauses'. In C, if you want to use feature of stdio, you have
to include it. VHDL is really more permissive.
It is a problem for VHDL users ?
Suggestion: add a 'with clause'.

Tristan.
Received on Wed Dec 1 05:07:50 2004