move and change

chapter2/Exercises.idr

@@ -0,0 +1,34 @@
+module Exercises
+
+-- 1, 2, 3, 4, 5
+palindrome : Nat -> String -> Bool
+palindrome n str = let halfs = splitHalf (toLower str) in
+                    length str > n && fst halfs == (reverse (snd halfs))
+  where
+    halfLength : String -> Nat
+    halfLength str = (length str) `div` 2
+
+    splitHalf : String -> (String, String)
+    splitHalf str = let firstHalf = substr 0 (halfLength str) str
+                        startIndex = if even (length str) then halfLength str else halfLength str + 1
+                        secondHalf = substr startIndex (length str) str in
+                        (firstHalf, secondHalf)
+      where
+        even : Nat -> Bool
+        even n = n `mod` 2 == 0
+
+-- 6
+counts : String -> (Nat, Nat)
+counts str = (length (words str), length str)
+
+-- 7
+top_ten : Ord a => List a -> List a
+top_ten xs = take 10 (reverse (sort xs))
+
+-- 8
+over_length : Nat -> List String -> Nat
+over_length n xs = let filtered = filter (\str => length str > n) xs in
+                       length filtered
+
+-- 9
+-- not now