Initial data commit

Task/CUSIP/Haskell/cusip-1.hs

@@ -0,0 +1,44 @@
+import Data.List(elemIndex)
+
+data Result = Valid | BadCheck | TooLong | TooShort | InvalidContent deriving Show
+
+-- convert a list of Maybe to a Maybe list.
+-- result is Nothing if any of values from the original list are Nothing
+allMaybe :: [Maybe a] -> Maybe [a]
+allMaybe = sequence
+
+toValue :: Char -> Maybe Int
+toValue c = elemIndex c $ ['0'..'9'] ++ ['A'..'Z'] ++ "*@#"
+
+-- check a list of ints to see if they represent a valid CUSIP
+valid :: [Int] -> Bool
+valid ns0 =
+    let -- multiply values with even index by 2
+        ns1 = zipWith (\i n -> (if odd i then n else 2*n)) [1..] $ take 8 ns0
+
+        -- apply div/mod formula from site and sum up results
+        sm = sum $ fmap (\s -> ( s `div` 10 ) + s `mod` 10) ns1
+
+    in  -- apply mod/mod formula from site and compare to last value in list
+        ns0!!8 == (10 - (sm `mod` 10)) `mod` 10
+
+-- check a String to see if it represents a valid CUSIP
+checkCUSIP :: String -> Result
+checkCUSIP cs
+       | l < 9     = TooShort
+       | l > 9     = TooLong
+       | otherwise = case allMaybe (fmap toValue cs) of
+                         Nothing -> InvalidContent
+                         Just ns -> if valid ns then Valid else BadCheck
+    where l = length cs
+
+testData =
+    [ "037833100"
+    , "17275R102"
+    , "38259P508"
+    , "594918104"
+    , "68389X106"
+    , "68389X105"
+    ]
+
+main = mapM_ putStrLn (fmap (\s -> s ++ ": " ++ show (checkCUSIP s)) testData)