On Sun, Dec 29, 2013 at 12:27 PM, Massimiliano Tomassoli <kiuhn...@gmail.com > wrote:
> What's the difference between protocols and simple overloading? > Dynamic dispatch. Overloading uses just the static type for dispatch, so this Java code: aBase = new Base(); aDerived = new Derived(); aBase2 = aDerived; something.foo(aBase); something.foo(aBase2); something.foo(aDerived); will call the same version of foo the first two times, though the third time it might call a different overload of foo (if there's a separate foo(Derived x) method in the class of "something"). Dynamic dispatch uses the runtime type. In Java you get this when you call aBase.bar(); aBase2.bar(); aDerived.ber(); and (if Derived overrides bar) get the Derived version of bar called for the second as well as the third calls, because aBase2's runtime type is Derived. Clojure protocols dispatch on the runtime type of the first argument, much like (non-static) Java methods (with "this" considered to be the first argument). Clojure multimethods can dispatch on the runtime type (or even other characteristics) of *all* of the arguments. I don't think anything Clojure does dispatches on the static type of anything, only on the number of arguments and sometimes on runtime types or other information, with the exception of some built-in inline functions (arithmetic +, for example) on primitive numeric arguments, and possibly also macros that encounter primitives. Indeed, primitive locals are just about the only static types to be found in Clojure (notwithstanding core.typed, whose use AFAIK does not influence the dispatch semantics of anything). -- -- 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/groups/opt_out.
