free-functors 0 → 0.1

raw patch · 5 files changed

+39/−11 lines, 5 filesdep +voidPVP ok

version bump matches the API change (PVP)

Dependencies added: void

API changes (from Hackage documentation)

Files

• examples/FreeNum.hs +32/−0
• examples/NonEmptyList.hs +1/−4
• free-functors.cabal +3/−2
• src/Data/Functor/Free.hs +3/−0
• src/Data/Functor/HFree.hs +0/−5

@@ -0,0 +1,32 @@+{-# LANGUAGE FlexibleInstances #-}+module FreeNum where++import Data.Functor.Free++import Control.Applicative++instance Num (Free Num a) where+  Free l + Free r = Free $ (+) <$> l <*> r+  Free l * Free r = Free $ (*) <$> l <*> r+  Free l - Free r = Free $ (-) <$> l <*> r+  negate (Free f) = Free $ negate <$> f+  abs (Free f)    = Free $ abs <$> f+  signum (Free f) = Free $ signum <$> f+  fromInteger i   = Free $ pure (fromInteger i)++x, y :: Free Num String+x = return "x"+y = return "y"++expr :: Free Num String+expr = 1 + x * (3 - y)++-- Monadic bind is variable substitution+subst :: Free Num String -> Free Num a+subst e = e >>= \v -> case v of +  "x" -> 10+  _   -> 2++-- Closed expressions can be evaluated to any other instance of Num+result :: Int+result = convertClosed (subst expr)

@@ -1,7 +1,4 @@-{-# LANGUAGE-    MultiParamTypeClasses-  , FlexibleInstances-  #-}+{-# LANGUAGE FlexibleInstances #-} module NonEmptyList where  import Data.Functor.Free

@@ -1,5 +1,5 @@ name:                free-functors-version:             0+version:             0.1 synopsis:            Provides free functors that are adjoint to functors that forget class constraints.  description:         A free functor is a left adjoint to a forgetful functor. It used to be the case                      that the only category that was easy to work with in Haskell was Hask itself, so@@ -42,7 +42,8 @@     base >= 4.4 && < 5,     constraints >= 0.3.2 && < 0.4,     transformers >= 0.2.0.0 && < 0.4,-    comonad >= 3.0 && < 3.1+    comonad >= 3.0 && < 3.1,+    void >= 0.4 && < 0.6  source-repository head   type:     git

@@ -32,6 +32,7 @@ import Data.Functor.Compose import Data.Foldable import Data.Traversable+import Data.Void   -- | The free functor for constraint @c@.@@ -88,3 +89,5 @@ convert :: (c (f a), Applicative f) => Free c a -> f a convert = rightAdjunct pure +convertClosed :: c x => Free c Void -> x+convertClosed = rightAdjunct absurd

@@ -3,10 +3,6 @@   , RankNTypes   , TypeOperators   , FlexibleInstances-  , GADTs-  , MultiParamTypeClasses-  , UndecidableInstances-  , ScopedTypeVariables   #-} ----------------------------------------------------------------------------- -- |@@ -26,7 +22,6 @@ ----------------------------------------------------------------------------- module Data.Functor.HFree where   -import Control.Monad import Control.Applicative import Control.Monad.Trans.Class