[fpc-pascal] Extending an enumeration

[Mark Morgan Lloyd]

Thierry Coq wrote:
> On 18/07/2010 20:56, Mark Morgan Lloyd wrote:
> ...
>> Yes, I was thinking that. However if the basic class was say a 
>> round-robin scheduler with phases rrQuiescent and rrInitialised and 
>> the descendant was say an HP comms protocol handler with additional 
>> phases hpReceivingPadding, hpReceivedSync and so on it would seem to 
>> be questionable practice to have to define all possible enumerated 
>> values in the basic class.
>>
> ...
> In this case, enumeration cannot be extended. If you look at it from an 
> analysis point of view, you're implementing a state machine with an 
> enumeration. If your state machine is extendable instead of fixed, and 
> you want to add substates to it, then a possible implementation is to 
> define a state class:

I agree, but that's more a poor choice of example on my part than an 
invalidation of the original question.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]