On Wed, Feb 17, 2010 at 3:49 PM, Tom Van Cutsem <[email protected]> wrote:
> [...] > >> 5) I've lost track of where Harmony is heading with classes, but do you >> have any thoughts on that? Do you see you traits as an alternative to any >> other class proposal, or would it be intended as an extension of classes (as >> the original traits proposal was), should they ever arrive? >> > > I'm glad you ask this question. To be frank, I don't see what benefits > classes would bring in addition to traits. > 1) As a unit of code reuse, trait composition is more flexible than class > inheritance. > 2) As a unit of encapsulation, closures are more flexible than private > instance variables. > 3) As a unit of instantiation, 'maker' functions are more flexible than > class constructors. > 4) As a unit of implementation sharing, traits have the same properties as > classes, given a trait-aware implementation. > 5) As a unit of classification, interface types are more flexible than > class types (of course ES doesn't have interfaces, so I think a solid > object-type-testing mechanism would be a more useful addition to ES than > classes would be). > [Numbers added to list entries above] Hi Tom, I love the elegance of this answer. I agree with your conclusion, and I agree with the above list regarding Java-like, Smalltalk-like, or ES4-like classes. However, on points #2 and #3, your traits proposal is identical to my classes-as-sugar proposal. > > In the original traits model, since traits are stateless, classes play an > additional role not fulfilled by traits: carrying instance variables. > However, in an extended trait model such as this one that allows traits to > define instance variables as well as methods, traits can now take over this > role from classes as well. > > Please do correct me if I'm missing a role for which classes do provide > significant added value. > > Cheers, > Tom > > >> P T Withington >> OpenLaszlo.ORG/Laszlo Systems >> >> >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > -- Cheers, --MarkM
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