IEEE 200X Fast Track Change Proposal

ID:	  FT-10

Proposer:     Jim Lewis, jim@synthworks.com 

Status:       Proposed
Proposed:     -
Analyzed:     Date
Resolved:     Date

Enhancement Summary:     Make Selected signal assignment constructs 
                         usable in sequential statements for both 
                         variables and signals.
                         
Related issues:          
Relevant LRM section:    

Enhancement Detail:
----------------------------
Current code:
stateProc : process
begin
  wait until rising_edge(Clk) ;
  if nReset = '0' then 
    State <= S0 ;
  else 
    case State is
      when S0 =>       State <= S1 ;
      when S1 =>       State <= S2 ;
      when S2 =>       State <= S3 ;
      when others =>   State <= S0 ;
    end case ; 
  end if ; 
end process ; 


Replacement code:
stateProc : process
begin
  wait until rising_edge(Clk) ;
  if nReset = '0' then 
    State <= S0 ;
  else 
    with State select
      State <= 
        S1 when S0,
        S2 when S1, 
        S3 when S2, 
        S0 when others ;
  end if ; 
end process ; 


Allow conditional_expression if it is included in 
parentheses.

stateProc : process
begin
  wait until rising_edge(Clk) ;
  if nReset = '0' then 
    State <= S0 ;
  else 
    with State select
      State <= 
        (S1 when I='1' else S0) when S0,
        (S2 when I='1' else S1) when S1, 
        (S3 when I='1' else S2) when S2, 
        S0 when others ;
  end if ; 
end process ; 




Analysis:
----------------------------
Modifications to 1076-2002
Move clause 9.5.2 to clause 8.4 (signal assignment)

Add similar copy clause 9.5.2 to clause 8.5 (variable assignment)
and minor tweak it for variable assignment.
This includes the following:

selected_variable_assignment ::=
  with expression select
    target <= options selected_expression ;

selected_expression ::=
    { expression when choices , }
    expression when choices

Editors note, expression is intended to include
conditional_expression if conditional_expression
is included in parentheses.



Resolution:
----------------------------
[To be performed by the 200X Fast Track Working Group]