Add remaining haskell book exercises

Haskell-book/18/Bind.hs

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+module Bind where
+
+import Control.Monad
+
+bind :: Monad m => (a -> m b) -> m a -> m b
+bind f x = join $ fmap f x

Haskell-book/18/Functions.hs

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+module Functions where
+
+j :: Monad m => m (m a) -> m a
+j = flip (>>=) id
+
+l1 :: Monad m => (a -> b) -> m a -> m b
+l1 = fmap
+
+l2 :: Monad m => (a -> b -> c) -> m a -> m b -> m c
+l2 f xs ys = f <$> xs <*> ys
+
+a :: Monad m => m a -> m (a -> b) -> m b
+a xs f = f <*> xs
+
+meh :: Monad m => [a] -> (a -> m b) -> m [b]
+meh xs f = rec $ fmap f xs
+    where rec [] = return []
+          rec (x:xs) = (:) <$> x <*> (rec xs)
+
+flipType :: Monad m => [m a] -> m [a]
+flipType = flip meh id

Haskell-book/18/Instance/.gitignore

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+.stack-work/
+Instance.cabal
+*~

Haskell-book/18/Instance/Setup.hs

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+import Distribution.Simple
+main = defaultMain

Haskell-book/18/Instance/package.yaml

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+name:                Instance
+version:             0.1.0.0
+github:              "githubuser/Instance"
+license:             BSD3
+author:              "Eugen Wissner"
+maintainer:          "belka@caraus.de"
+copyright:           "2018 Eugen Wissner"
+
+dependencies:
+- base >= 4.7 && < 5
+- QuickCheck
+- checkers
+
+library:
+  source-dirs: src
+
+tests:
+  Instance-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - Instance

Haskell-book/18/Instance/src/Identity.hs

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+module Identity where
+
+import Test.QuickCheck
+import Test.QuickCheck.Checkers
+
+newtype Identity a = Identity a
+    deriving (Eq, Ord, Show)
+
+instance Functor Identity where
+    fmap f (Identity x) = Identity $ f x
+
+instance Applicative Identity where
+    pure = Identity
+    (Identity f) <*> x = fmap f x
+
+instance Monad Identity where
+    return = pure
+    (Identity x) >>= f = f x
+
+instance Arbitrary a => Arbitrary (Identity a) where
+    arbitrary = fmap Identity $ arbitrary
+
+instance Eq a => EqProp (Identity a) where
+    (=-=) = eq

Haskell-book/18/Instance/src/List.hs

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+module List where
+
+import Test.QuickCheck
+import Test.QuickCheck.Checkers
+
+data List a =
+    Nil
+  | Cons a (List a)
+  deriving (Eq, Show)
+
+instance Functor List where
+    fmap f Nil = Nil
+    fmap f (Cons x xs) = Cons (f x) (fmap f xs)
+
+append :: List a -> List a -> List a
+append Nil ys = ys
+append (Cons x xs) ys = Cons x $ xs `append` ys
+
+fold :: (a -> b -> b) -> b -> List a -> b
+fold _ b Nil = b
+fold f b (Cons h t) = f h (fold f b t)
+
+concat' :: List (List a) -> List a
+concat' = fold append Nil
+
+flatMap :: (a -> List b) -> List a -> List b
+flatMap f as = concat' $ fmap f as
+
+instance Applicative List where
+    pure f = Cons f Nil
+    Nil <*> _ = Nil
+    _ <*> Nil = Nil
+    f <*> x = flatMap (\f' -> fmap f' x) f
+
+instance Monad List where
+    return = pure
+    x >>= f = concat' $ fmap f x
+
+instance Arbitrary a => Arbitrary (List a) where
+    arbitrary = frequency [(1, pure Nil),
+                           (5, Cons <$> arbitrary <*> arbitrary)]
+
+instance Eq a => EqProp (List a) where
+    (=-=) = eq

Haskell-book/18/Instance/src/Nope.hs

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+module Nope where
+
+import Test.QuickCheck
+import Test.QuickCheck.Checkers
+
+data Nope a = NopeDotJpg deriving (Show, Eq)
+
+instance Functor Nope where
+    fmap _ _ = NopeDotJpg
+
+instance Applicative Nope where
+    pure _ = NopeDotJpg
+    _ <*> _ = NopeDotJpg
+
+instance Monad Nope where
+    return _ = NopeDotJpg
+    _ >>= _ = NopeDotJpg
+
+instance Arbitrary (Nope a) where
+    arbitrary = return NopeDotJpg
+
+instance EqProp (Nope a) where
+    (=-=) = eq

Haskell-book/18/Instance/src/PhhhbbtttEither.hs

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+{-# LANGUAGE NoImplicitPrelude #-}
+module PhhhbbtttEither where
+
+import Prelude ( Monad(..)
+               , Functor(..)
+               , Applicative(..)
+               , Eq(..)
+               , ($)
+               , Show(..) )
+import Test.QuickCheck
+import Test.QuickCheck.Checkers
+
+data PhhhbbtttEither b a =
+        Left a
+      | Right b
+      deriving (Eq, Show)
+
+instance Functor (PhhhbbtttEither b) where
+    fmap f (Right x) = Right x
+    fmap f (Left x) = Left $ f x
+
+instance Applicative (PhhhbbtttEither b) where
+    pure x = Left x
+    Right f <*> _ = Right f
+    Left f <*> x = fmap f x
+
+instance Monad (PhhhbbtttEither b) where
+    return = pure
+    (Right x) >>= f = Right x
+    (Left x) >>= f = f x
+
+instance (Arbitrary a, Arbitrary b) => Arbitrary (PhhhbbtttEither b a) where
+    arbitrary = frequency [ (1, fmap Right arbitrary)
+                          , (1, fmap Left arbitrary)
+                          ]
+
+instance (Eq a, Eq b) => EqProp (PhhhbbtttEither b a) where
+    (=-=) = eq

Haskell-book/18/Instance/src/Sum.hs

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+module Sum where
+
+import Test.QuickCheck
+import Test.QuickCheck.Checkers
+
+data Sum a b =
+    First a
+  | Second b
+  deriving (Eq, Show)
+
+instance Functor (Sum a) where
+    fmap f (First x) = First x
+    fmap f (Second x) = Second $ f x
+
+instance Applicative (Sum a) where
+    pure x = Second x
+    First f <*> _ = First f
+    Second f <*> x = fmap f x
+
+instance Monad (Sum a) where
+    return = pure
+    (First x) >>= f = First x
+    (Second x) >>= f = f x
+
+instance (Arbitrary a, Arbitrary b) => Arbitrary (Sum a b) where
+    arbitrary = frequency [ (1, fmap First arbitrary)
+                          , (1, fmap Second arbitrary)
+                          ]
+
+instance (Eq a, Eq b) => EqProp (Sum a b) where
+    (=-=) = eq

Haskell-book/18/Instance/stack.yaml

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+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+# resolver: ghcjs-0.1.0_ghc-7.10.2
+# resolver:
+#  name: custom-snapshot
+#  location: "./custom-snapshot.yaml"
+resolver: lts-10.4
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+# - location:
+#    git: https://github.com/commercialhaskell/stack.git
+#    commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+# - location: https://github.com/commercialhaskell/stack/commit/e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#   extra-dep: true
+#  subdirs:
+#  - auto-update
+#  - wai
+#
+# A package marked 'extra-dep: true' will only be built if demanded by a
+# non-dependency (i.e. a user package), and its test suites and benchmarks
+# will not be run. This is useful for tweaking upstream packages.
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver
+# (e.g., acme-missiles-0.3)
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=1.6"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

Haskell-book/18/Instance/test/Spec.hs

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+import Sum
+import Nope
+import qualified PhhhbbtttEither as Phhhbbttt
+import Identity
+import List
+import Test.QuickCheck.Checkers
+import Test.QuickCheck.Classes
+
+main :: IO ()
+main = do
+    quickBatch $ functor $ (First (1, 2, 3) :: Sum (Int, Int, Int) (Int, Int, Int))
+    quickBatch $ applicative $ (First (1, 2, 3) :: Sum (Int, Int, Int) (Int, Int, Int))
+    quickBatch $ monad $ (First (1, 2, 3) :: Sum (Int, Int, Int) (Int, Int, Int))
+
+    quickBatch $ functor $ (NopeDotJpg :: Nope (Int, Int, Int))
+    quickBatch $ applicative $ (NopeDotJpg :: Nope (Int, Int, Int))
+    quickBatch $ monad $ (NopeDotJpg :: Nope (Int, Int, Int))
+
+    quickBatch $ functor $ (Phhhbbttt.Left (1, 2, 3) :: Phhhbbttt.PhhhbbtttEither (Int, Int, Int) (Int, Int, Int))
+    quickBatch $ applicative $ (Phhhbbttt.Left (1, 2, 3) :: Phhhbbttt.PhhhbbtttEither (Int, Int, Int) (Int, Int, Int))
+    quickBatch $ monad $ (Phhhbbttt.Left (1, 2, 3) :: Phhhbbttt.PhhhbbtttEither (Int, Int, Int) (Int, Int, Int))
+
+    quickBatch $ functor $ (Identity (1, 2, 3) :: Identity (Int, Int, Int))
+    quickBatch $ applicative $ (Identity (1, 2, 3) :: Identity (Int, Int, Int))
+    quickBatch $ monad $ (Identity (1, 2, 3) :: Identity (Int, Int, Int))
+
+    quickBatch $ functor (Cons (1 :: Integer, 2 :: Integer, 3 :: Integer) Nil)
+    quickBatch $ applicative (Cons (1 :: Integer, 2 :: Integer, 3 :: Integer) Nil)
+    quickBatch $ monad (Cons (1 :: Integer, 2 :: Integer, 3 :: Integer) Nil)