Add the haskell book

1 files changed, 30 insertions, 0 deletions

diff --git a/Haskell-book/08/src/WordNumber.purs b/Haskell-book/08/src/WordNumber.purs
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+++ b/Haskell-book/08/src/WordNumber.purs
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+module WordNumber where
+
+import Data.Array (reverse)
+import Data.Maybe (Maybe(..))
+import Data.String (joinWith)
+import Data.Tuple (Tuple(..))
+import Data.Unfoldable (unfoldr)
+import Prelude
+
+digitToWord :: Int -> String
+digitToWord 0 = "null"
+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 -> Array Int
+digits n = reverse $ unfoldr unfold n
+    where unfold x
+              | x == 0    = Nothing
+              | otherwise = Just (Tuple (mod x 10) (div x 10))
+
+wordNumber :: Int -> String
+wordNumber n = joinWith "-" $ map digitToWord (digits n)