complete predicate exercises

src/predicates.clj

@@ -1,41 +1,46 @@
 (ns predicates)
 
 (defn sum-f [f g x]
-  :-)
+  (+ (f x) (g x)))
 
 (defn less-than [n]
-  :-)
+  (fn [k] (< k n)))
 
 (defn equal-to [n]
-  :-)
+  (fn [k] (== k n)))
 
 (defn set->predicate [a-set]
-  :-)
+  (fn [x] (contains? a-set x)))
 
 (defn pred-and [pred1 pred2]
-  :-)
+  (fn [x] (and (pred1 x) (pred2 x))))
 
 (defn pred-or [pred1 pred2]
-  :-)
+  (fn [x] (or (pred1 x) (pred2 x))))
 
 (defn whitespace? [character]
   (Character/isWhitespace character))
 
 (defn blank? [string]
-  :-)
+  (or (empty? string) (every? whitespace? string)))
 
 (defn has-award? [book award]
-  :-)
+  (contains? (:awards book) award))
 
 (defn HAS-ALL-THE-AWARDS? [book awards]
-  :-)
+  (every? (:awards book) awards))
 
 (defn my-some [pred a-seq]
-  :-)
+  (first (filter identity (map pred a-seq))))
 
 (defn my-every? [pred a-seq]
-  :-)
+  ;; (= (filter pred a-seq) a-seq)
+  ;; this is slightly better because it can early exit
+  (empty? (filter (complement pred) a-seq))
+  )
 
 (defn prime? [n]
-  :-)
+  (and (>= n 2)
+       (let [divides? (fn [x] (zero? (mod n x)))]
+         (not (some divides? (range 2 n))))))
 ;^^