Re: Re: Registries [2]

At 13:51 2003-07-28, David Abrahams wrote:
>Daniel Wallin <[email protected]> writes:
>
> > At 10:20 2003-07-28, Daniel Wallin wrote:
> >>At 01:10 2003-07-28, David Abrahams wrote:
> >>>Oh.  The implicit imports I thought we'd handle by having a global
> >>>converter registration chain for any type and simply tacking it onto
> >>>the end of each extension's local chain as part of the initialization
> >>>of the local registration.
> >>
> >>Right, but this seems to imply the same implementation that I suggested.
> >>Because even if module Y is initialized after module X, module X needs
> >>to know about the converters module Y exposes. So the initialization of
> >>module Y needs to add converters do module X's registry. Right?
> >
> > I think I misinterpreted this, did you mean linking the actual chains 
> together
> > rather than adding converters from the global chain to the local ones?
>
>Yes, I meant essentially that all local chains for a type would share
>a tail: the corresponding global chain.

Ok, I've been thinking about this.

The biggest problem I can see with this is that we can't eliminate duplicate
converters, if a module registers a converter for type X it will get a 
duplicate
in the global chain. Of course things will still work as expected, but
overload resolution will suffer in terms of performance since we'd need to
try more converters before we can conclude that there's no match.

Also, identical converters registered by multiple modules can't be separated,
so we'd end up with a lot of identical converters for primitive types.
I guess we could keep all primitive converters in the shared library.
This is an issue with automatic importing in general though.

Thoughts?

---
Daniel Wallin



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