diff --git a/.travis.yml b/.travis.yml
index 455f3c0..45c29f6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 language: clojure
-lein: lein2
-script: lein2 midje :config .midje-grading-config.clj
+lein: lein
+script: lein midje :config .midje-grading-config.clj
 jdk:
   - openjdk7
 notifications:
diff --git a/src/recursion.clj b/src/recursion.clj
index 95d77aa..bcb1bc1 100644
--- a/src/recursion.clj
+++ b/src/recursion.clj
@@ -1,92 +1,189 @@
 (ns recursion)
 
 (defn product [coll]
-  :-)
+  (if (empty? coll)
+    1
+    (* (first coll)
+       (product (rest coll)))))
 
 (defn singleton? [coll]
-  :-)
+  (and (not (empty? coll)) (empty? (rest coll))))
 
 (defn my-last [coll]
-  :-)
+  (if (empty? (rest coll))
+    (first coll)
+    (my-last (rest coll))))
 
 (defn max-element [a-seq]
-  :-)
+  (cond
+    (empty? a-seq)
+      nil
+    (empty? (rest a-seq))
+      (first a-seq)
+    :else
+      (max (first a-seq) (max-element (rest a-seq)))))
 
 (defn seq-max [seq-1 seq-2]
-  [:-])
+  (if (> (count seq-1) (count seq-2)) seq-1 seq-2))
 
 (defn longest-sequence [a-seq]
-  [:-])
+  (if (empty? a-seq)
+    nil
+    (seq-max (first a-seq) (longest-sequence (rest a-seq)))))
 
 (defn my-filter [pred? a-seq]
-  [:-])
+  (if (empty? a-seq)
+    a-seq
+    (let [f (first a-seq)
+          r (my-filter pred? (rest a-seq))]
+      (if (pred? f) (cons f r) r))))
 
 (defn sequence-contains? [elem a-seq]
-  :-)
+  (cond
+    (empty? a-seq)
+      false
+    (== (first a-seq) elem)
+      true
+    :else
+      (sequence-contains? elem (rest a-seq))))
 
 (defn my-take-while [pred? a-seq]
-  [:-])
+  (cond
+    (empty? a-seq)
+      a-seq
+    (pred? (first a-seq))
+      (cons (first a-seq) (my-take-while pred? (rest a-seq)))
+    :else
+      []))
 
 (defn my-drop-while [pred? a-seq]
-  [:-])
+  (cond
+    (empty? a-seq)
+      a-seq
+    (pred? (first a-seq))
+      (my-drop-while pred? (rest a-seq))
+    :else
+      a-seq))
 
 (defn seq= [a-seq b-seq]
-  :-)
+  (cond
+    (and (empty? a-seq) (empty? b-seq)) true
+    (or (empty? a-seq) (empty? b-seq)) false
+    (= (first a-seq) (first b-seq)) (seq= (rest a-seq) (rest b-seq))
+    :else false))
 
 (defn my-map [f seq-1 seq-2]
-  [:-])
+  (if
+    (or (empty? seq-1) (empty? seq-2)) []
+    (cons (f (first seq-1) (first seq-2)) (my-map f (rest seq-1) (rest seq-2)))))
 
 (defn power [n k]
-  :-)
+  (if (zero? k)
+    1
+    (* n (power n (dec k)))))
 
 (defn fib [n]
-  :-)
+  (if (< n 2)
+    n
+    (+ (fib (dec (dec n))) (fib (dec n)))))
 
 (defn my-repeat [how-many-times what-to-repeat]
-  [:-])
+  (if (< how-many-times 1)
+    []
+    (cons what-to-repeat (my-repeat (dec how-many-times) what-to-repeat))))
 
 (defn my-range [up-to]
-  [:-])
+  (if (< up-to 1)
+    []
+    (let [n (dec up-to)]
+      (cons n (my-range n)))))
 
 (defn tails [a-seq]
-  [:-])
+  (if (empty? a-seq)
+    [[]]
+    (cons a-seq (tails (rest a-seq)))))
 
 (defn inits [a-seq]
-  [:-])
+  (reverse (map reverse (tails (reverse a-seq)))))
 
 (defn rotations [a-seq]
-  [:-])
+  (if (empty? a-seq)
+    [[]]
+    (map concat (rest (tails a-seq)) (rest (inits a-seq)))))
 
 (defn my-frequencies-helper [freqs a-seq]
-  [:-])
+  (if (empty? a-seq)
+    freqs
+    (let [elem (first a-seq)
+          new-count (if (contains? freqs elem)
+                      (inc (get freqs elem))
+                      1)
+          new-freqs (assoc freqs elem new-count)]
+      (my-frequencies-helper new-freqs (rest a-seq)))))
 
 (defn my-frequencies [a-seq]
-  [:-])
+  (my-frequencies-helper {} a-seq))
 
+;(defn un-frequencies [a-map]
+;  (apply concat (map repeat (vals a-map) (keys a-map))))
 (defn un-frequencies [a-map]
-  [:-])
+  (if (empty? a-map)
+    []
+    (let [[val num] (first a-map)]
+      (concat (repeat num val) (un-frequencies (rest a-map))))))
 
 (defn my-take [n coll]
-  [:-])
+  (if (or (< n 1) (empty? coll))
+    ()
+    (cons (first coll) (my-take (dec n) (rest coll)))))
 
 (defn my-drop [n coll]
-  [:-])
+  (if (or (< n 1) (empty? coll))
+    coll
+    (my-drop (dec n) (rest coll))))
 
 (defn halve [a-seq]
-  [:-])
+  (let [n (int (/ (count a-seq) 2))]
+    [(my-take n a-seq) (my-drop n a-seq)]))
 
 (defn seq-merge [a-seq b-seq]
-  [:-])
+  (cond
+    (empty? a-seq) b-seq
+    (empty? b-seq) a-seq
+    :else (let [a (first a-seq)
+                b (first b-seq)]
+            (if (< a b)
+              (cons a (seq-merge (rest a-seq) b-seq))
+              (cons b (seq-merge a-seq (rest b-seq)))))))
 
 (defn merge-sort [a-seq]
-  [:-])
+  (if (< (count a-seq) 2)
+    a-seq
+    (let [[seq1 seq2] (halve a-seq)]
+      (seq-merge (merge-sort seq1) (merge-sort seq2)))))
 
 (defn split-into-monotonics [a-seq]
-  [:-])
+  (if (empty? a-seq)
+    ()
+    (let [init-list (rest (inits a-seq))
+          my-sorted? (fn [s] (let [ss (sort s)] (or (seq= ss s) (seq= ss (reverse s)))))
+          num-sorted (count (take-while my-sorted? init-list))
+          mono (take num-sorted a-seq)]
+      (cons (take num-sorted a-seq) (split-into-monotonics (drop num-sorted a-seq))))))
+
+(defn permutations [a-seq]
+  (if (empty? a-seq)
+    [[]]
+    (let [rest-perms (permutations (rest a-seq))
+          mapped (map #(cons (first a-seq) %) rest-perms)]
+      (mapcat rotations mapped))))
 
-(defn permutations [a-set]
-  [:-])
 
 (defn powerset [a-set]
-  [:-])
+  (if (empty? a-set)
+    #{#{}}
+    (let [rest-pset (powerset (rest a-set))
+          joined (set (map #(conj % (first a-set)) rest-pset))]
+      (clojure.set/union rest-pset joined))))
+