converted lazy seqs to functions so they won't hold their heads

3 files changed, 48 insertions, 18 deletions

diff --git a/src/clojure/contrib/lazy_seqs.clj b/src/clojure/contrib/lazy_seqs.clj
index 118a5602..cf83b5de 100644
--- a/src/clojure/contrib/lazy_seqs.clj
+++ b/src/clojure/contrib/lazy_seqs.clj
@@ -33,24 +33,32 @@
 (ns clojure.contrib.lazy-seqs
   (:use clojure.contrib.def))
 
+; primes cannot be written efficiently as a function, because
+; it needs to look back on the whole sequence. contrast with
+; fibs and powers-of-2 which only need a fixed buffer of 1 or 2
+; previous values.
 (defvar primes
-  (lazy-cat [2 3 5 7]
+  (concat 
+   [2 3 5 7]
+   (lazy-seq
     (let [primes-from
-          (fn primes-from [n [f & r]]
-            (if (some #(zero? (rem n %))
-                      (take-while #(<= (* % %) n) primes))
-              (recur (+ n f) r)
-              (lazy-seq (cons n (primes-from (+ n f) r)))))
-          wheel (cycle [2 4 2 4 6 2 6 4 2 4 6 6 2 6  4  2
-                        6 4 6 8 4 2 4 2 4 8 6 4 6 2  4  6
-                        2 6 6 4 2 4 6 2 6 4 2 4 2 10 2 10])]
-      (primes-from 11 wheel)))
-  "A lazy sequence of all the prime numbers.")
+	  (fn primes-from [n [f & r]]
+	    (if (some #(zero? (rem n %))
+		      (take-while #(<= (* % %) n) primes))
+	      (recur (+ n f) r)
+	      (lazy-seq (cons n (primes-from (+ n f) r)))))
+	  wheel (cycle [2 4 2 4 6 2 6 4 2 4 6 6 2 6  4  2
+			6 4 6 8 4 2 4 2 4 8 6 4 6 2  4  6
+			2 6 6 4 2 4 6 2 6 4 2 4 2 10 2 10])]
+      (primes-from 11 wheel))))
+  "Lazy sequence of all the prime numbers.")
+
+(defn fibs []
+  "Returns a lazy sequence of all the Fibonacci numbers."
+  (map first (iterate (fn [[a b]] [b (+ a b)]) [0 1])))
+
+(defn powers-of-2 []
+  "Returns a lazy sequence of all the powers of 2"
+  (iterate #(bit-shift-left % 1) 1))
 
-(defvar fibs
-  (lazy-cat [0 1] (map + fibs (rest fibs)))
-  "A lazy sequence of all the fibonacci numbers.")
 
-(defvar powers-of-2
-  (lazy-seq (cons 1 (map #(bit-shift-left % 1) powers-of-2)))
-  "A lazy sequence of all the powers of 2")
diff --git a/src/clojure/contrib/test_contrib.clj b/src/clojure/contrib/test_contrib.clj
index 0aa7432d..7c1444e0 100644
--- a/src/clojure/contrib/test_contrib.clj
+++ b/src/clojure/contrib/test_contrib.clj
@@ -17,7 +17,8 @@
   (:gen-class))
 
 (def test-names [:complex-numbers :monads :pprint.pretty :pprint.cl-format
-                 :str-utils :shell-out :test-graph :test-dataflow :test-java-utils])
+                 :str-utils :shell-out :test-graph :test-dataflow :test-java-utils
+		 :test-lazy-seqs])
 
 (def test-namespaces
      (map #(symbol (str "clojure.contrib.test-contrib." (name %)))
diff --git a/src/clojure/contrib/test_contrib/test_lazy_seqs.clj b/src/clojure/contrib/test_contrib/test_lazy_seqs.clj
new file mode 100644
index 00000000..3bf4ba78
--- /dev/null
+++ b/src/clojure/contrib/test_contrib/test_lazy_seqs.clj
@@ -0,0 +1,21 @@
+(ns clojure.contrib.test-contrib.test-lazy-seqs
+  (:use clojure.contrib.test-is
+	clojure.contrib.lazy-seqs))
+
+(deftest test-fibs
+  (is (= [0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765 10946 
+	    17711 28657 46368 75025 121393 196418 317811 514229 832040 1346269 2178309 
+	    3524578 5702887 9227465 14930352 24157817 39088169 63245986 102334155 
+	    165580141 267914296 433494437 701408733 1134903170 1836311903 2971215073 
+	    4807526976 7778742049]
+	 (take 50 (fibs)))))
+
+(deftest test-powers-of-2
+  (is (= [1 2 4 8 16 32 64 128 256 512]
+	 (take 10 (powers-of-2)))))
+
+(deftest test-primes
+  (is (= [2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 
+	  103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 
+	  199 211 223 227 229]
+	 (take 50 primes))))