2 files changed, 127 insertions, 0 deletions
diff --git a/src/clojure/contrib/greatest_least.clj b/src/clojure/contrib/greatest_least.clj
new file mode 100644
index 00000000..10c7eae6
--- /dev/null
+++ b/src/clojure/contrib/greatest_least.clj
@@ -0,0 +1,62 @@
+(ns clojure.contrib.greatest-least)
+
+(defn- boundary
+  [cmp-fn f & args]
+  (when args
+    (reduce (fn [a b] (if (cmp-fn (compare (f b) (f a)))
+                        b
+                        a)) args)))
+
+(defn greatest-by
+  "Return the argument for which f yields the greatest value."
+  [f & args]
+  (apply boundary pos? f args))
+
+(defn greatest
+  "Return the greatest argument."
+  [& args]
+  (apply greatest-by identity args))
+
+(defn least-by
+  "Return the argument for which f yields the smallest value."
+  [f & args]
+  (apply boundary neg? f args))
+
+(defn least
+  "Return the smallest element."
+  [& args]
+  (apply least-by identity args))
+
+
+(defn- boundary-all
+  [cmp-fn f & args]
+  (when args
+    (reduce (fn [a b]
+              (if (nil? a)
+                (cons b nil)
+                (let [x (compare (f b) (f (first a)))]
+                  (cond (zero? x) (cons b a)
+                        (cmp-fn x) (cons b nil)
+                        :else a))))
+            nil
+            args)))
+
+(defn all-greatest-by
+  "Return all the elements for which f yields the greatest value."
+  [f & args]
+  (apply boundary-all pos? f args))
+
+(defn all-greatest
+  "Returns all the greatest elements."
+  [& args]
+  (apply all-greatest-by identity args))
+
+(defn all-least-by
+  "Return all the elements for which f yields the least value."
+  [f & args]
+  (apply boundary-all neg? f args))
+
+(defn all-least
+  "Returns all the least elements."
+  [& args]
+  (apply all-least-by identity args))
diff --git a/src/clojure/contrib/test_contrib/greatest_least.clj b/src/clojure/contrib/test_contrib/greatest_least.clj
new file mode 100644
index 00000000..557c0a3c
--- /dev/null
+++ b/src/clojure/contrib/test_contrib/greatest_least.clj
@@ -0,0 +1,65 @@
+(ns clojure.contrib.test-contrib.greatest-least
+  (:use clojure.contrib.greatest-least
+        [clojure.contrib.test-is :only (is deftest run-tests)]))
+
+(deftest test-greatest
+  (is (nil? (greatest)) "greatest with no arguments is nil")
+  (is (= 1 (greatest 1)))
+  (is (= 2 (greatest 1 2)))
+  (is (= 2 (greatest 2 1)))
+  (is (= "b" (greatest "aa" "b"))))
+
+(deftest test-greatest-by
+  (is (nil? (greatest-by identity)) "greatest-by with no arguments is nil")
+  (is (= "" (greatest-by count "")))
+  (is (= "a" (greatest-by count "a" "")))
+  (is (= "a" (greatest-by count "" "a")))
+  (is (= "aa" (greatest-by count "aa" "b"))))
+
+(deftest test-least
+  (is (nil? (least)) "least with no arguments is nil")
+  (is (= 1 (least 1)))
+  (is (= 1 (least 1 2)))
+  (is (= 1 (least 2 1)))
+  (is (= "aa" (least "aa" "b"))))
+
+(deftest test-least-by
+  (is (nil? (least-by identity)) "least-by with no arguments is nil")
+  (is (= "" (least-by count "")))
+  (is (= "" (least-by count "a" "")))
+  (is (= "" (least-by count "" "a")))
+  (is (= "b" (least-by count "aa" "b"))))
+
+(deftest test-all-greatest
+  (is (nil? (all-greatest)) "all-greatest with no arguments is nil")
+  (is (= (list 1) (all-greatest 1)))
+  (is (= (list 1 1) (all-greatest 1 1)))
+  (is (= (list 2) (all-greatest 2 1 1)))
+  (is (= (list 2) (all-greatest 1 2 1)))
+  (is (= (list 2) (all-greatest 1 1 2)))
+  (is (= (list :c) (all-greatest :b :c :a))))
+
+(deftest test-all-greatest-by
+  (is (nil? (all-greatest-by identity)) "all-greatest-by with no arguments is nil")
+  (is (= (list "a")) (all-greatest-by count "a"))
+  (is (= (list "a" "a")) (all-greatest-by count "a" "a"))
+  (is (= (list "aa")) (all-greatest-by count "aa" "b"))
+  (is (= (list "aa")) (all-greatest-by count "b" "aa" "c"))
+  (is (= (list "cc" "aa")) (all-greatest-by count "aa" "b" "cc")))
+
+(deftest test-all-least
+  (is (nil? (all-least)) "all-least with no arguments is nil")
+  (is (= (list 1) (all-least 1)))
+  (is (= (list 1 1) (all-least 1 1)))
+  (is (= (list 1 1) (all-least 2 1 1)))
+  (is (= (list 1 1) (all-least 1 2 1)))
+  (is (= (list 1 1) (all-least 1 1 2)))
+  (is (= (list :a) (all-least :b :c :a))))
+
+(deftest test-all-least-by
+  (is (nil? (all-least-by identity)) "all-least-by with no arguments is nil")
+  (is (= (list "a")) (all-least-by count "a"))
+  (is (= (list "a" "a")) (all-least-by count "a" "a"))
+  (is (= (list "b")) (all-least-by count "aa" "b"))
+  (is (= (list "c" "b")) (all-least-by count "b" "aa" "c"))
+  (is (= (list "b")) (all-least-by count "aa" "b" "cc")))