finished exercises for Course.Anagrams and Course.FastAnagrams

README.markdown

@@ -35,6 +35,6 @@ After this, the following progression of modules is recommended:
 * `Course.MoreParser` -> Done
 * `Course.JsonParser` -> Done
 * `Course.Interactive` -> Done
-* `Course.Anagrams`
-* `Course.FastAnagrams`
+* `Course.Anagrams` -> Done
+* `Course.FastAnagrams` -> Done
 * `Course.Cheque`

src/Course/Anagrams.hs

@@ -7,7 +7,11 @@ module Course.Anagrams where
 import Course.Core
 import Course.List
 import Course.Functor
+import Course.Monad
 
+import Course.Applicative
+import Course.Traversable
+import Course.Optional
 {-
 
 Functions you will need
@@ -32,13 +36,17 @@ anagrams ::
   Chars
   -> Filename
   -> IO (List Chars)
-anagrams =
-  error "todo: Course.Anagrams#anagrams"
+anagrams ls flName = do
+  content <- readFile flName
+  return $ intersectBy equalIgnoringCase (words content) (permutations ls)
+
 
 -- Compare two strings for equality, ignoring case
 equalIgnoringCase ::
   Chars
   -> Chars
   -> Bool
-equalIgnoringCase =
-  error "todo: Course.Anagrams#equalIgnoringCase"
+equalIgnoringCase Nil Nil = True
+equalIgnoringCase _ Nil = False
+equalIgnoringCase Nil _ = False
+equalIgnoringCase (a:.as) (b:.bs) = (toLower a == toLower b) && equalIgnoringCase as bs

src/Course/FastAnagrams.hs

@@ -8,14 +8,22 @@ import Course.List
 import Course.Functor
 import qualified Data.Set as S
 
+import Course.Monad
+
+import Course.Applicative
+import Course.Traversable
+import Course.Optional
+
 -- Return all anagrams of the given string
 -- that appear in the given dictionary file.
 fastAnagrams ::
   Chars
   -> Filename
   -> IO (List Chars)
-fastAnagrams =
-  error "todo: Course.FastAnagrams#fastAnagrams"
+fastAnagrams ls flName = do
+  content <- readFile flName
+  let dicSet = S.fromList (hlist (words content))
+  return $ foldLeft (\acc x -> if x `S.member` dicSet then x:.acc else acc) Nil (permutations ls)
 
 newtype NoCaseString =
   NoCaseString {