tasks a-s

Task/Range-extraction/Haskell/range-extraction-1.hs

@@ -0,0 +1,13 @@
+import Data.List (intercalate)
+
+extractRange :: [Int] -> String
+extractRange = intercalate "," . f
+  where f :: [Int] -> [String]
+        f (x1 : x2 : x3 : xs) | x1 + 1 == x2 && x2 + 1 == x3
+             = (show x1 ++ '-' : show xn) : f xs'
+          where (xn, xs') = g (x3 + 1) xs
+                g a (n : ns) | a == n    = g (a + 1) ns
+                             | otherwise = (a - 1, n : ns)
+                g a []                   = (a - 1, [])
+        f (x : xs)            = show x : f xs
+        f []                  = []

Task/Range-extraction/Haskell/range-extraction-2.hs

@@ -0,0 +1,2 @@
+> extractRange $ [0..2] ++ 4 : [6..8] ++ 11 : 12 : [14..25] ++ [27..33] ++ [35..39]
+"0-2,4,6-8,11,12,14-25,27-33,35-39"