add third exercise of lecture 7

2 files changed, 23 insertions, 0 deletions

diff --git a/lec07/JoinList.hs b/lec07/JoinList.hs
index ccfa838..5e1949f 100644
--- a/lec07/JoinList.hs
+++ b/lec07/JoinList.hs
@@ -1,6 +1,7 @@
 module JoinList where
 
 import Sized
+import Scrabble
 
 data JoinList m a = Empty
                   | Single m a
diff --git a/lec07/Scrabble.hs b/lec07/Scrabble.hs
new file mode 100644
index 0000000..2c3b1f9
--- /dev/null
+++ b/lec07/Scrabble.hs
@@ -0,0 +1,22 @@
+module Scrabble where
+import Data.Char
+import Data.List ((!?))
+
+-- Exercise 3
+
+newtype Score = Score Int
+  deriving (Eq, Ord, Show, Num)
+
+-- Needed due to changes in the standard library, see Sized.
+instance Semigroup Score where
+  (<>) = (+)
+
+instance Monoid Score where
+  mempty = Score 0
+
+score :: Char -> Score
+score c = Score $ fromMaybe 0 $ scores !? (fromEnum (toUpper c) - fromEnum 'A')
+  where scores = [1,3,3,2,1,4,2,4,1,8,5,1,3,1,1,3,10,1,1,1,1,4,4,8,4,10] :: [Int]
+
+scoreString :: String -> Score
+scoreString = foldl' <> mempty