filter and Draw Something word finder.

src/cljc/cljc/core.cljc

@@ -487,6 +487,11 @@
     false
     true))
 
+(defn ^boolean empty?
+  "Returns true if coll has no items - same as (not (seq coll)).
+  Please use the idiom (seq x) rather than (not (empty? x))"
+  [coll] (not (seq coll)))
+
 (defn ^boolean set?
   "Returns true if x satisfies ISet"
   [x]
@@ -566,6 +571,16 @@
 
 (defn identity [x] x)
 
+(defn filter
+  "Returns a lazy sequence of the items in coll for which
+  (pred item) returns true. pred must be free of side-effects."
+  ([pred coll]
+     (when-let [s (seq coll)]
+       (let [f (first s) r (rest s)]
+         (if (pred f)
+           (cons f (filter pred r))
+           (filter pred r))))))
+
 (defn flatten-tail
   [coll]
   (if-let [n (next coll)]

test/clojurec/core_test.clj

@@ -364,4 +364,25 @@
 	    1 2 3 4 0 -1 1 2 3 4 0 5 -1 1 2 3 4 0 5 6 -1
 	    1 2 3 4 5 0 -1 1 2 3 4 5 0 6 -1]))))
 
+(deftest programs
+  (testing "somewhat useful programs"
+    (is (= (core-run '(do
+                        (defn remove-one [coll o]
+                          (loop [rev ()
+                                 coll (seq coll)]
+                            (if coll
+                              (let [f (first coll)]
+                                (if (= o f)
+                                  (concat rev (next coll))
+                                  (recur (cons f rev) (next coll))))
+                              rev)))
+
+                        (defn check-word [len chars word]
+                          (and (= len (count word))
+                               (empty? (reduce remove-one word chars))))
+
+                        (pr (filter (fn [word] (check-word 3 "abcdef" word))
+                                    (list "bad" "leg" "its" "gig" "gag" "bag" "fad")))))
+           ['(bad fad)]))))
+
 ;;(run-tests *ns*)