Add collatz-conjecture

Author: koladilip

collatz-conjecture/src/CollatzConjecture.hs

@@ -1,15 +1,12 @@
 module CollatzConjecture (collatz) where
 
-collatz_internal :: Integer -> Integer
-collatz_internal num 
-    | num == 1 =  0
-    | isEven = 1 + collatz_internal (num `div` 2)
-    | otherwise = 1 + collatz_internal (3 * num + 1)
-    where
-        isEven = rem num 2 == 0
-
 collatz :: Integer -> Maybe Integer
 collatz num
     | num > 0 =  Just (collatz_internal num)
     | otherwise = Nothing
+    where 
+        collatz_internal pnum 
+            | pnum == 1 =  0
+            | even pnum = 1 + collatz_internal (pnum `div` 2)
+            | otherwise = 1 + collatz_internal (3 * pnum + 1)