Migrated generic.functor

src/main/clojure/clojure/algo/generic/functor.clj

@@ -0,0 +1,39 @@
+;; Generic interface for functors
+
+;; by Konrad Hinsen
+
+;; Copyright (c) Konrad Hinsen, 2009-2011. All rights reserved.  The use
+;; and distribution terms for this software are covered by the Eclipse
+;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+;; which can be found in the file epl-v10.html at the root of this
+;; distribution.  By using this software in any fashion, you are
+;; agreeing to be bound by the terms of this license.  You must not
+;; remove this notice, or any other, from this software.
+
+(ns
+  ^{:author "Konrad Hinsen"
+     :doc "Generic functor interface (fmap)"}
+  clojure.algo.generic.functor)
+
+
+(defmulti fmap
+  "Applies function f to each item in the data structure s and returns
+   a structure of the same kind."
+   {:arglists '([f s])}
+   (fn [f s] (type s)))
+
+(defmethod fmap clojure.lang.IPersistentList
+  [f v]
+  (map f v))
+
+(defmethod fmap clojure.lang.IPersistentVector
+  [f v]
+  (into (empty v) (map f v)))
+
+(defmethod fmap clojure.lang.IPersistentMap
+  [f m]
+  (into (empty m) (for [[k v] m] [k (f v)])))
+
+(defmethod fmap clojure.lang.IPersistentSet
+  [f s]
+  (into (empty s) (map f s)))

src/test/clojure/clojure/algo/generic/test_functor.clj

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+;; Test routines for clojure.algo.generic.collection
+
+;; Copyright (c) Konrad Hinsen, 2011. All rights reserved.  The use
+;; and distribution terms for this software are covered by the Eclipse
+;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+;; which can be found in the file epl-v10.html at the root of this
+;; distribution.  By using this software in any fashion, you are
+;; agreeing to be bound by the terms of this license.  You must not
+;; remove this notice, or any other, from this software.
+
+(ns clojure.algo.generic.test-functor
+  (:use [clojure.test :only (deftest is are run-tests)])
+  (:require [clojure.algo.generic.functor :as gf])
+  (:require [clojure.algo.generic.collection :as gc]))
+
+; Test implementations for CLojure's built-in collections
+(deftest builtin-collections
+  (are [a b] (= a b)
+       (gf/fmap inc (list 1 2 3)) (list 2 3 4)
+       (gf/fmap inc [1 2 3]) [2 3 4]
+       (gf/fmap inc {:A 1 :B 2 :C 3}) {:A 2 :B 3 :C 4}
+       (gf/fmap inc #{1 2 3}) #{2 3 4}))
+
+
+; Define a multiset class. The representation is a map from values to counts.
+(defrecord multiset [map])
+
+(defn mset
+  [& elements]
+  (gc/into (new multiset {}) elements))
+
+; Implement the collection multimethods.
+(defmethod gc/conj multiset
+  ([ms x]
+   (let [msmap (:map ms)]
+     (new multiset (assoc msmap x (inc (get msmap x 0))))))
+  ([ms x & xs]
+   (reduce gc/conj (gc/conj ms x) xs)))
+
+(defmethod gc/empty multiset
+  [ms]
+  (new multiset {}))
+
+(defmethod gc/seq multiset
+  [ms]
+  (apply concat (map (fn [[x n]] (repeat n x)) (:map ms))))
+
+; Implement fmap
+(defmethod gf/fmap multiset
+  [f m]
+  (gc/into (gc/empty m) (map f (gc/seq m))))
+
+; Multiset tests
+(deftest multiset-tests
+  (are [a b] (= a b)
+       (gf/fmap inc (mset 1 2 3)) (mset 2 3 4)))
+