9_b_4: Add solution

1 files changed, 0 insertions, 68 deletions

diff --git a/ch09/9_b_3.hs b/ch09/9_b_3.hs
deleted file mode 100644
index 882f7db..0000000
--- a/ch09/9_b_3.hs
+++ /dev/null
@@ -1,68 +0,0 @@
--- Take the predicates and combinators from "Gluing predicates together" on page
--- 224 and make them work with our new Info type.
-
-{-- From examples/examples/ch09/BetterPredicate.hs modified according to the assignment --}
-import Data.Time (UTCTime(..))
-import System.Directory (Permissions(..))
-import System.FilePath (takeExtension)
-
-
-data Info = Info {
-      infoPath :: FilePath
-    , infoPerms :: Maybe Permissions
-    , infoSize :: Maybe Integer
-    , infoModTime :: Maybe UTCTime
-    } deriving (Eq, Ord, Show)
-
-type InfoF a = Info -> a
-
-
-equalP :: (Eq a) => InfoF a -> a -> (InfoF Bool)
-equalP f k = (\info -> f info == k)
-
-equalP' :: (Eq a) => (InfoF a) -> a -> (InfoF Bool)
-equalP' f k info = (f info == k)
-
-liftP :: (a -> b -> Bool) -> (InfoF a) -> b -> (InfoF Bool)
-liftP q f k info = f info `q` k
-
-greaterP, lesserP :: (Ord a) => (InfoF a) -> a -> (InfoF Bool)
-greaterP = liftP (>)
-lesserP = liftP (<)
-
-simpleAndP :: (InfoF Bool) -> (InfoF Bool) -> (InfoF Bool)
-simpleAndP f g info = f info && g info
-
-liftP2 :: (a -> b -> Bool) -> (InfoF a) -> (InfoF b) -> (InfoF Bool)
-liftP2 q f g info = f info `q` g info
-
-andP = liftP2 (&&)
-orP = liftP2 (||)
-
-constP :: a -> (InfoF a)
-constP k _ = k
-
-liftP' q f k info = f info `q` constP k info
-
-liftPath :: (FilePath -> a) -> (InfoF a)
-liftPath f info = f (infoPath info)
-
-myTest2 = (liftPath takeExtension `equalP` ".cpp") `andP`
-          (infoSize `greaterP` (Just 131072))
-{-- End of code from examples --}
-
--- ghci> :l 9_b_3.hs
--- [1 of 1] Compiling Main             ( 9_b_3.hs, interpreted )
--- Ok, one module loaded.
-
--- ghci> infoA = Info "asdf.cpp" Nothing (Just 131072) Nothing
--- ghci> myTest2 infoA
--- False
-
--- ghci> infoB = Info "asdf.hs" Nothing (Just 131073) Nothing
--- ghci> myTest2 infoB
--- False
-
--- ghci> infoC = Info "asdf.cpp" Nothing (Just 131073) Nothing
--- ghci> myTest2 infoC
--- True