On Fri, May 02, 2008 at 12:21:27PM -0700, chromatic wrote: > On Friday 02 May 2008 11:55:54 Larry Wall wrote: > > > On Fri, May 02, 2008 at 11:15:34AM -0700, chromatic wrote: > > > : All classes imply the existence of a role of the same name. > > > If a role is derived from a class, it must of necessity be a snapshot > > of the class, because roles are immutable, while classes are not. > > Agreed. > > > The only interesting question in my mind is whether you can take > > another snapshot and override the previous one somehow, or whether > > such derived roles should version themselves so that the snapshots > > can be distinguished by longname. Alternately, we make one snapshot > > when a class is first composed, and refuse to make any other snapshots > > for that name regardless of how the class under that name changes. > > I'm not sure which is best. Snapshotting at the time of first composition > (or > the first time someone says "Hey, I provide that other class's role!") seems > right though.
I don't think that first composition is useful. If it's first composition, then if my code loads up a class, with the intention of extending it, then wants to pass it somewhere else that uses it as a role, then it fails. I'd have to declare an empty subclass of the (now modified) class, just to be allowed to make a role. And I think that this applies: On Fri, May 02, 2008 at 04:32:00PM -0700, chromatic wrote: > 2b) If the only way to declare that conformance is through subclassing, you > lose and I'll take your language designer license away*. > * Note that there is no language designer license. Yet. Although if, instead, it's first time that some code references that class as a role, I'm still a bit stuffed if the package that defines the class also manages to do something that references it as a role, and does it all before the BEGIN block of the use returns, and my code isn't able to add its modifications. Is there any way to pre-declare that I want to defer baking the role from a class? (Which I guess would make it an error to reference that role at run time in any way, until I'd issued a second declaration that I was done, and baking season is open) Nicholas Clark
