Add remaining haskell book exercises

1 files changed, 68 insertions, 0 deletions

diff --git a/Haskell-book/25/Bifunctor/src/Bifunctor.hs b/Haskell-book/25/Bifunctor/src/Bifunctor.hs
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+++ b/Haskell-book/25/Bifunctor/src/Bifunctor.hs
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+{-# LANGUAGE NoImplicitPrelude #-}
+module Bifunctor where
+
+import Prelude (($), id, (.))
+
+class Bifunctor p where
+    {-# MINIMAL bimap | first, second #-}
+
+    bimap :: (a -> b)
+          -> (c -> d)
+          -> p a c
+          -> p b d
+    bimap f g = first f . second g
+
+    first :: (a -> b) -> p a c -> p b c
+    first f = bimap f id
+
+    second :: (b -> c) -> p a b -> p a c
+    second = bimap id
+
+-- 1
+data Deux a b = Deux a b
+
+instance Bifunctor Deux where
+    first f (Deux a c) = Deux (f a) c
+    second f (Deux a b) = Deux a (f b)
+
+-- 2
+data Const a b = Const a
+
+instance Bifunctor Const where
+    first f (Const a) = Const (f a)
+    second f (Const a) = Const a
+
+-- 3
+data Drei a b c = Drei a b c
+
+instance Bifunctor (Drei a) where
+    first f (Drei a b c) = Drei a (f b) c
+    second f (Drei a b c) = Drei a b (f c)
+
+-- 4
+data SuperDrei a b c = SuperDrei a b
+
+instance Bifunctor (SuperDrei a) where
+    first f (SuperDrei a b) = SuperDrei a (f b)
+    second f (SuperDrei a b) = SuperDrei a b
+
+-- 5
+data SemiDrei a b c = SemiDrei a
+
+instance Bifunctor (SemiDrei a) where
+    first f (SemiDrei a) = SemiDrei a
+    second f (SemiDrei a) = SemiDrei a
+
+-- 6
+data Quadriceps a b c d = Quadzzz a b c d
+
+instance Bifunctor (Quadriceps a b) where
+    first f (Quadzzz a b c d) = Quadzzz a b (f c) d
+    second f (Quadzzz a b c d) = Quadzzz a b c (f d)
+
+-- 7
+data Either a b = Left a | Right b
+
+instance Bifunctor Either where
+    first f (Left a) = Left $ f a
+    second f (Right b) = Right $ f b
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