Add remaining haskell book exercises

3 files changed, 153 insertions, 0 deletions

diff --git a/Haskell-book/14/morse/src/Main.hs b/Haskell-book/14/morse/src/Main.hs
new file mode 100644
index 0000000..1f73b90
--- /dev/null
+++ b/Haskell-book/14/morse/src/Main.hs
@@ -0,0 +1,59 @@
+module Main where
+
+import Control.Monad (forever, when)
+import Data.List (intercalate)
+import Data.Traversable (traverse)
+import Morse (stringToMorse, morseToChar)
+import System.Environment (getArgs)
+import System.Exit (exitFailure, exitSuccess)
+import System.IO (hGetLine, hIsEOF, stdin)
+
+convertToMorse :: IO ()
+convertToMorse = forever $ do
+    weAreDone <- hIsEOF stdin
+    when weAreDone exitSuccess
+
+    line <- hGetLine stdin
+    convertLine line
+
+    where convertLine line = do
+            let morse = stringToMorse line
+            case morse of
+                (Just str) -> putStrLn (intercalate " " str)
+                Nothing -> do
+                    putStrLn $ "ERROR: " ++ line
+                    exitFailure
+
+convertFromMorse :: IO ()
+convertFromMorse = forever $ do
+    weAreDone <- hIsEOF stdin
+    when weAreDone exitSuccess
+
+    line <- hGetLine stdin
+    convertLine line
+
+    where
+        convertLine line = do
+            let decoded :: Maybe String
+                decoded = traverse morseToChar (words line)
+
+            case decoded of
+                (Just s) -> putStrLn s
+                Nothing -> do
+                    putStrLn $ "ERROR: " ++ line
+                    exitFailure
+
+main :: IO ()
+main = do
+    mode <- getArgs
+    case mode of
+        [arg] ->
+            case arg of
+                "from" -> convertFromMorse
+                "to" -> convertToMorse
+                _ -> argError
+        _ -> argError
+
+    where argError = do
+            putStrLn "Please specify the first argument as being 'from' or 'to' morse, such as: morse to"
+            exitFailure
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diff --git a/Haskell-book/14/morse/src/Morse.hs b/Haskell-book/14/morse/src/Morse.hs
new file mode 100644
index 0000000..03193e5
--- /dev/null
+++ b/Haskell-book/14/morse/src/Morse.hs
@@ -0,0 +1,68 @@
+module Morse
+       ( Morse
+       , charToMorse
+       , morseToChar
+       , stringToMorse
+       , letterToMorse
+       , morseToLetter
+       ) where
+
+import qualified Data.Map as M
+
+type Morse = String
+
+letterToMorse :: (M.Map Char Morse)
+letterToMorse = M.fromList [
+    ('a', ".-")
+  , ('b', "-...")
+  , ('c', "-.-.")
+  , ('d', "-..")
+  , ('e', ".")
+  , ('f', "..-.")
+  , ('g', "--.")
+  , ('h', "....")
+  , ('i', "..")
+  , ('j', ".---")
+  , ('k', "-.-")
+  , ('l', ".-..")
+  , ('m', "--")
+  , ('n', "-.")
+  , ('o', "---")
+  , ('p', ".--.")
+  , ('q', "--.-")
+  , ('r', ".-.")
+  , ('s', "...")
+  , ('t', "-")
+  , ('u', "..-")
+  , ('v', "...-")
+  , ('w', ".--")
+  , ('x', "-..-")
+  , ('y', "-.--")
+  , ('z', "--..")
+  , ('1', ".----")
+  , ('2', "..---")
+  , ('3', "...--")
+  , ('4', "....-")
+  , ('5', ".....")
+  , ('6', "-....")
+  , ('7', "--...")
+  , ('8', "---..")
+  , ('9', "----.")
+  , ('0', "-----")
+  ]
+
+morseToLetter :: M.Map Morse Char
+morseToLetter =
+    M.foldWithKey (flip M.insert) M.empty
+                  letterToMorse
+
+charToMorse :: Char -> Maybe Morse
+charToMorse c =
+    M.lookup c letterToMorse
+
+stringToMorse :: String -> Maybe [Morse]
+stringToMorse s =
+    sequence $ fmap charToMorse s
+
+morseToChar :: Morse -> Maybe Char
+morseToChar m = M.lookup m morseToLetter
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diff --git a/Haskell-book/14/morse/src/WordNumber.hs b/Haskell-book/14/morse/src/WordNumber.hs
new file mode 100644
index 0000000..5b25ee2
--- /dev/null
+++ b/Haskell-book/14/morse/src/WordNumber.hs
@@ -0,0 +1,26 @@
+module WordNumber where
+
+import Data.List (unfoldr, intercalate)
+import Data.Maybe (Maybe(..))
+
+digitToWord :: Int -> String
+digitToWord 0 = "zero"
+digitToWord 1 = "one"
+digitToWord 2 = "two"
+digitToWord 3 = "three"
+digitToWord 4 = "four"
+digitToWord 5 = "five" 
+digitToWord 6 = "six"
+digitToWord 7 = "seven"
+digitToWord 8 = "eight"
+digitToWord 9 = "nine"
+digitToWord _ = ""
+
+digits :: Int -> [Int]
+digits n = reverse $ unfoldr unfold n
+    where unfold x
+                | x == 0    = Nothing
+                | otherwise = Just ((mod x 10), (div x 10))
+
+wordNumber :: Int -> String
+wordNumber n = intercalate "-" $ map digitToWord (digits n)
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