Add the haskell book

6 files changed, 139 insertions, 0 deletions

diff --git a/Haskell-book/07/src/ArtfulDodgy.purs b/Haskell-book/07/src/ArtfulDodgy.purs
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+++ b/Haskell-book/07/src/ArtfulDodgy.purs
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+module ArtfulDodgy where
+
+import Prelude
+
+-- Exercise 1
+dodgy :: Int -> Int -> Int
+dodgy x y = x + y * 10
+
+oneIsOne :: Int -> Int
+oneIsOne = dodgy 1
+
+oneIsTwo :: Int -> Int
+oneIsTwo = (flip dodgy) 2
diff --git a/Haskell-book/07/src/CasePractice.purs b/Haskell-book/07/src/CasePractice.purs
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+++ b/Haskell-book/07/src/CasePractice.purs
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+module CasePractice where
+
+import Data.Int (even)
+import Prelude
+
+-- Exercise 1
+functionC :: forall a. Ord a => a -> a -> a
+functionC x y = case (x > y) of
+    true -> x
+    false -> y
+
+-- Exercise 2
+isEvenAdd2 :: Int -> Int
+isEvenAdd2 n = case even n of
+    true -> n + 2
+    false -> n
+
+-- Exercise 3
+nums :: Int -> Int
+nums x =
+    case compare x 0 of
+         LT -> -1
+         GT -> 1
+         EQ -> 0
diff --git a/Haskell-book/07/src/Ex.purs b/Haskell-book/07/src/Ex.purs
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+++ b/Haskell-book/07/src/Ex.purs
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+module Ex where
+
+import Data.Int (fromString)
+import Data.Maybe (Maybe(..))
+import Data.Tuple (Tuple(..))
+import Prelude
+import Unsafe.Coerce (unsafeCoerce)
+
+--
+-- Multiple choice
+--
+-- Exercise 2
+f :: Char -> String
+f = unsafeCoerce unit
+
+g :: String -> Array String
+g = unsafeCoerce unit
+
+e :: Char -> Array String
+e = g <<< f
+
+-- Exercise 5
+f' :: forall a. a -> a
+f' x = x
+
+g' :: Boolean
+g' = f' true
+
+--
+-- Let's write code
+--
+
+-- Exercise 1
+tensDigit :: Int -> Int
+tensDigit x = d
+    where xLast = x `div` 10
+          d     = xLast `mod` 10
+
+-- Exercise 2
+hunsD :: Int -> Int
+hunsD x = d
+    where xLast = x `div` 100
+          d     = xLast `mod` 10
+
+foldBool :: forall a. a -> a -> Boolean -> a
+foldBool x y z = case z of
+    false -> x
+    true  -> y
+
+findBool2 :: forall a. a -> a -> Boolean -> a
+findBool2 x y z
+    | z         = y
+    | otherwise = x
+
+foldBool3 :: forall a. a -> a -> Boolean -> a
+foldBool3 x _ false = x
+foldBool3 _ y true  = y
+
+-- Exercise 3
+g'' :: forall a b c. (a -> b) -> Tuple a c -> Tuple b c
+g'' f'' (Tuple a c) = Tuple (f'' a) c
+
+-- Exercise 5
+-- id :: a -> a
+-- id = x = x
+
+roundTrip :: Int -> Int
+roundTrip = fromMaybe <<< fromString <<< show
+    where fromMaybe (Just n) = n
+          fromMaybe Nothing = unsafeCoerce unit
diff --git a/Haskell-book/07/src/GrabBag.purs b/Haskell-book/07/src/GrabBag.purs
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+++ b/Haskell-book/07/src/GrabBag.purs
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+module GrabBags where
+
+import Data.Int (odd)
+import Prelude
+
+-- 3 a)
+addOneIfOdd :: Int -> Int
+addOneIfOdd n = case odd n of
+    true -> f n
+    false -> n
+    where f = \k -> k + 1
+
+addFive :: (Int -> (Int -> Int))
+addFive = \x -> \y -> (if x > y then y else x) + 5
diff --git a/Haskell-book/07/src/Main.purs b/Haskell-book/07/src/Main.purs
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+++ b/Haskell-book/07/src/Main.purs
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+module Main where
+
+import Prelude
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (CONSOLE, log)
+
+main :: forall e. Eff (console :: CONSOLE | e) Unit
+main = do
+    log (id "4")
diff --git a/Haskell-book/07/src/VarietyPack.purs b/Haskell-book/07/src/VarietyPack.purs
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+++ b/Haskell-book/07/src/VarietyPack.purs
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+module VarietyPack where
+
+import Data.Tuple (Tuple(..))
+
+f :: forall a b c d e g
+   . Tuple (Tuple a b) c
+  -> Tuple (Tuple d e) g
+  -> Tuple (Tuple a d) (Tuple c g)
+f (Tuple (Tuple a b) c) (Tuple (Tuple d e) g) = Tuple (Tuple a d) (Tuple c g)