Re: [myhdl-list] Proposal: SignalType symbol

[Christopher L. F. <chr...@gm...>]

On 6/11/2010 4:19 AM, Jan Decaluwe wrote:
> Christopher Felton wrote:
>    
>>       >  Your factory function Signal() must return the correct class object
>>       >  based upon the parameters passed to it.
>>       >
>>       >  So Signal is just a function now that returns a class object so
>>      there is
>>       >  no such thing as an instance of it.
>>
>>      Right. For completeness, there is still the guarantee that any returned
>>      object will be of type SignalType (so that the corresponding isinstance
>>      check will always be true), but the specific subtype depends on the
>>      parameters.
>>
>>
>> Ok, I am  going to back up and make sure I understand this.
>>
>> We have a base class, *Signal(...)* and derived classes DelayedSignal,
>> ShadowSignal, etc.  As you mentioned some earlier design decision guided
>> this path.  From a users point of view the desired effect is that they
>> only care about a *Signal* that may have some different attributes but
>> the user doesn't need to know that it is a different object (just
>> refreshing and sync'n out loud).
>>
>> Now we have a factory function (introduced with the ShadowSignal) and a
>> proposed SignalType.  The SignalType exposes the actual base class
>> *_Signal_* because we can't have an instance of the factory function
>> (well you can but that is not the use here).  So the SignalType property
>> exposes the base class so we identify variable's types.
>>      
> Correct. In effect, we decouple the interface to create Signal objects
> from their base class SignalType. Everywhere where you tested where
> an instance is a Signal, it should merely be a matter of using SignalType
> instead.
>
> Should I already push this change to the public repo's for experimenting?
>
>
>    
Yes, sounds good to me

>
>