generic: new module comparison plus general support code

1 files changed, 36 insertions, 0 deletions

diff --git a/src/clojure/contrib/generic.clj b/src/clojure/contrib/generic.clj
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+;; Support code for generic interfaces
+
+(ns clojure.contrib.generic
+  "Generic interface support code
+
+   NOTE: This library is VERY experimental. It WILL change significantly
+   with future release."
+  (:use [clojure.contrib.types :only (defadt)]))
+
+;
+; A dispatch function that separates nulary, unary, binary, and
+; higher arity calls and also selects on type for unary and binary
+; calls.
+;
+(defn nary-dispatch
+  ([] ::nulary)
+  ([x] (type x))
+  ([x y]
+     [(type x) (type y)])
+  ([x y & more] ::nary))
+
+;
+; We can't use [::binary :default], so we need to define a root type
+; of the type hierarcy. The derivation for Object covers all classes,
+; but all non-class types will need an explicit derive clause.
+; Ultimately, a macro might take care of this.
+;
+(def root-type ::any)
+(derive Object root-type)
+
+;
+; Symbols referring to ::nulary and ::n-ary
+;
+(def nulary-type ::nulary)
+(def nary-type ::nary)
+