fix syntax of most functions in lecture 7's exercises

1 files changed, 12 insertions, 11 deletions

diff --git a/lec07/JoinList.hs b/lec07/JoinList.hs
index 61df8da..4eba3d2 100644
--- a/lec07/JoinList.hs
+++ b/lec07/JoinList.hs
@@ -1,5 +1,7 @@
 module JoinList where
 
+import Sized
+
 data JoinList m a = Empty
                   | Single m a
                   | Append m (JoinList m a) (JoinList m a)
@@ -9,11 +11,11 @@ data JoinList m a = Empty
 
 tag :: Monoid m => JoinList m a -> m
 tag Empty = mempty
-tag Single m _ = m
-tag Append m _ _ = m
+tag (Single m _) = m
+tag (Append m _ _) = m
 
 (+++) :: Monoid m => JoinList m a -> JoinList m a -> JoinList m a
-(+++) jl1 jl2 = mappend jl1 jl2
+(+++) jl1 jl2 = Append (mappend (tag jl1) (tag jl2)) jl1 jl2
 
 -- Exercise 2
 
@@ -23,10 +25,10 @@ indexJ n (Single _ a)
        | n == 0 = Just a
        | otherwise = Nothing
 indexJ n (Append m jl1 jl2)
-       | n < 0 || n >= m = Nothing
-       | n < tag1 = indexJ n jl1
-       | n >= tag1 = indexJ (n - tag1) jl2
-       where tag1 = tag jl1
+       | n < 0 || n >= (getSize $ size m) = Nothing
+       | n < s1 = indexJ n jl1
+       | n >= s1 = indexJ (n - s1) jl2
+       where s1 = getSize $ size $ tag jl1
 
 dropJ :: (Sized b, Monoid b) => Int -> JoinList b a -> JoinList b a
 dropJ _ Empty = Empty
@@ -35,7 +37,6 @@ dropJ n jl
 dropJ n (Single _ _)
       | n >= 1 = Empty
 dropJ n (Append m jl1 jl2)
-      | n >= m = Empty
-      | n >= tag1 = jl2
-      where tag1 = tag jl1
-
+      | n >= (getSize $ size m) = Empty
+      | n >= s1 = jl2
+      where s1 = getSize $ size $ tag jl1