The attached patch to clojure.core implements an optional universal parent type for Clojure hierarchies and defines such a type for the global default hierarchy. With this patch applied, Clojure passes the test_clojure and test_contrib test suites in clojure.contrib. I also tested it with all my own code.
The changes in detail: 1) make-hierarchy now takes as an optional argument the root type of the hierarchy. It is stored under the key :root. 2) derive preserves the :root key in the hierarchy map. 3) global-hierarchy is created with :root as its root type. The use of an unqualified keyword is not a mistake: by using a type that derive would refuse it makes sure that no one can tamper with the root type in any way. 4) isa? returns true if its parent argument is the root type of the hierarchy, no matter what the argument child is. This puts the root type above everything, including Object. These changes would already be sufficient to get the functionality I wanted for multimethods. However, for consistency I also modified parents, ascendants, and descendants to create the coherent view that the root type is every other type's parent: 5) parents adds the root type (if defined) to its result set for any argument except the root type. 6) ancestors adds the root type (if defined) to its result set for any argument except the root type. 7) descendants returns the set of all types in the hierarchy if its argument is the root type. I added one more fix to this patch: 8) The docstring of defmulti now says that the optional hierarchy argument must be a var referring to a hierarchy, rather than the hierarchy itself. Here is an example of what becomes possible with this patch: (defmulti plus (fn [x y] [(type x) (type y)])) (defmethod plus :default [x y] "default") (defmethod plus [java.lang.Number java.lang.Number] [x y] "two numbers") (defmethod plus [:root java.lang.Number] [x y] "x anything, y number") (defmethod plus [java.lang.Number :root] [x y] "x number, y anything") (plus 1 2) (plus 'x 2) (plus 1 "abc") (plus 'x 'y) Konrad. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
root-type.patch
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