Add the haskell book

3 files changed, 102 insertions, 0 deletions

diff --git a/Haskell-book/06/src/EqInstances.purs b/Haskell-book/06/src/EqInstances.purs
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+module EqInstances where
+    -- Exercise: Eq Instances
+    -- p. 178
+
+import Prelude
+
+-- Ex. 1
+data TisAnInteger =
+    TisAn Int
+
+instance eqTisAn :: Eq TisAnInteger where
+    eq x y = x == y
+
+-- Ex. 2
+data TwoIntegers =
+    Two Int Int
+
+instance ewTwoIntegers :: Eq TwoIntegers where
+    eq (Two x y) (Two x' y') = x == x' && y == y'
+
+-- Ex. 3
+data StringOrInt =
+    TisAnInt Int
+  | TisAString String
+
+instance eqStringOrInt :: Eq StringOrInt where
+    eq (TisAnInt x) (TisAnInt y) = x == y
+    eq (TisAString x) (TisAString y) = x == y
+    eq _ _ = false
+
+-- Ex. 4
+data Pair a =
+    Pair a a
+
+instance eqPair :: Eq a => Eq (Pair a) where
+    eq (Pair a b) (Pair a' b') = a == a' && b == b'
+
+-- Ex. 5
+data Tuple a b =
+    Tuple a b
+
+instance eqTuple :: (Eq a, Eq b) => Eq (Tuple a b) where
+    eq (Tuple a b) (Tuple a' b') = a == a' && b == b'
+
+-- Ex. 6
+data Which a =
+    ThisOne a
+  | ThatOne a
+
+instance eqWhich :: Eq a => Eq (Which a) where
+    eq (ThisOne x) (ThisOne y) = x == y
+    eq (ThatOne x) (ThatOne y) = x == y
+    eq _ _ = false
+
+-- Ex. 7
+data EitherOr a b =
+    Hello a
+  | Goodbye b
+
+instance eqEitherOr :: (Eq a, Eq b) => Eq (EitherOr a b) where
+    eq (Hello _) (Goodbye _) = false
+    eq (Goodbye _) (Hello _) = false
+    eq _ _ = true
diff --git a/Haskell-book/06/src/Ex.purs b/Haskell-book/06/src/Ex.purs
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+++ b/Haskell-book/06/src/Ex.purs
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+module Ex where
+
+import Prelude
+
+--
+-- Type-Kwon-Do Two: Electric Typealoo
+--
+chk :: forall a b. Eq b => (a -> b) -> a -> b -> Boolean
+chk f a b = (f a) == b
diff --git a/Haskell-book/06/src/Main.purs b/Haskell-book/06/src/Main.purs
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+++ b/Haskell-book/06/src/Main.purs
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+module Main where
+
+import Prelude
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (CONSOLE, log)
+
+data DayOfWeek =
+    Mon | Tue | Weds | Thu | Fri | Sat | Sun
+
+data Date =
+    Date DayOfWeek Int
+
+instance eqDayOfWeek :: Eq DayOfWeek where
+    eq Mon Mon = true
+    eq Tue Tue = true
+    eq Weds Weds = true
+    eq Thu Thu = true
+    eq Fri Fri = true
+    eq Sat Sat = true
+    eq Sun Sun = true
+    eq _ _ = false
+
+instance eqDate :: Eq Date where
+    eq (Date weekday dayOfMonth)
+       (Date weekday' dayOfMonth') =
+        weekday == weekday' && dayOfMonth == dayOfMonth'
+
+main :: forall e. Eff (console :: CONSOLE | e) Unit
+main = do
+  log "Hello sailor!"