On Friday, January 23, 2015 at 3:13:08 PM UTC-5, Tassilo Horn wrote: > > philli...@newcastle.ac.uk <javascript:> (Phillip Lord) writes: > > >> I use satisfies? for optional features, e.g., if some data structure > >> satisfies some protocol, then that optional feature is enabled, else > >> it's disabled. But that's not really on a hot path so I don't care > >> much about satisfies? performance. > > > > Have you tried just implementing the protocol over Object to do > > nothing? Then putting use an alternative implementation of the > > protocol where you want. > > I really use it for optional features for which no alternative > implementation exists. Concretely, I have a library that can work with > several graph data structures in a uniform way. Some of them have > first-class edges, others only have references. For example, my lib has > a code generation facility where there's some code like > > (when (satisfies? IEdges type-graph) > (generate-edge-access-fns ...)) > > But for other stuff I do extend protocols to Object (and nil) providing > a default implementation. > > Bye, > Tassilo >
One approach is to have a first-class-edges? method in the mother graph protocol. Another is to have such a method in IEdges and extend that to Object with first-class-edges? returning false and the other IEdges-specific methods throwing IllegalStateExceptions, as well as to "true" IEdges subtypes with the first returning true and the rest doing whatever they should do. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
