On Wed, Mar 25, 2009 at 1:44 AM, Konrad Hinsen <konrad.hin...@laposte.net> wrote: > Could you elaborate a bit on this? I haven't met any major obstacles > with multimethods yet. The dispatch functions give quite a lot of > flexibility in practice. In what situation did you find them > inconvenient?
To summarize, I think the points that have been raised here and on related threads are that: 1. Structs don't inherently have a type. If you want to dispatch on type (a common use-case), you have to make a constructor that inserts the type information as part of the struct. Some have expressed concern that it may be too easy for this "type information" to be altered, or worse, the data could be "changed" or "removed" in a way that makes the struct inconsistent with the type label it carries around. 2. No way to call "next-method" or "super", which limits the ability to reuse related methods. 3. The dispatch mechanism requires a lot of explicit prefer-methods, or else it may be hard to guarantee you won't get a run-time error from a situation the dispatch system considers ambiguous. This also makes code less extensible because to add a method, you must know about all the other methods that have been implemented in order to insert all the appropriate preferences. Honestly, the one time I used Clojure's multimethods (contrib.math), they suited my needs perfectly, but I definitely see where these concerns are coming from. The existing mechanism is very flexible in one respect: you can dispatch on anything you want, not just type. In other respects, it seems like Clojure's multimethods are less sophisticated than their CLOS/Dylan counterparts. If there is a way to achieve the same things in Clojure, it's not readily apparent (see recent thread about the next-method/super issue, for example). --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
