impl (empty) → 0.1.0.0

raw patch · 5 files changed

+118/−0 lines, 5 filesdep +basedep +impldep +named

Dependencies added: base, impl, named, template-haskell

Files

• Impl.hs +28/−0
• Impl/Utils.hs +26/−0
• example/Monad/Foo.hs +8/−0
• example/Monad/Impl.hs +15/−0
• impl.cabal +41/−0

@@ -0,0 +1,28 @@+{-# OPTIONS_HADDOCK show-extensions #-}+-- | This small but extensible framework facilitates defining complex defaulting rules that are not handled by @DefaultSignatures@, and reducing the overhead of giving instances to new datatypes by generating superclasses. One reason we might want this is when a superclass wants to be given a default by two different subclasses (ex: @Bifunctor@ and @Profunctor@ both could generate @Functor@ instances). See the @example@ internal library for how to implement instances of 'Impl'.+module Impl (Impl(..),NamedMethods+  -- * Reexports+  ,type (:->),TypeQ,(!) ,type (:!), NamedF(Arg), arg+  ) where+import Language.Haskell.TH+import Named hiding (Name)+import GHC.TypeLits (Symbol)+import Impl.Utils+ +class Impl c where+  type Methods c :: [Symbol]+  -- | Instantiate the implementing class along with all its superclasses+  -- Ex: +  --+  -- > impl @Monad [t|[]|]+  -- >   ! #return [|\x -> [x]|]+  -- >   ! #bind   [|flip concatMap|]+  impl :: TypeQ -> NamedMethods c :-> DecsQ++-- | +type family NamedExpQ ss where+  NamedExpQ '[] = '[]+  NamedExpQ (s ': ss) = (s :! ExpQ) ': NamedExpQ ss++-- | "Named" TH 'Exp's for the class method implementations+type NamedMethods c = NamedExpQ (Methods c)

@@ -0,0 +1,26 @@+module Impl.Utils where+import Language.Haskell.TH++typeList :: [Type] -> Type+typeList = foldr (\t -> AppT (AppT PromotedConsT t)) PromotedNilT++-- | Converts a variable number of arguments into curried form. Ex:+--+--  >>> :!kind '[Int,String,Double] :-> IO ()+--  Int -> String -> Double -> IO ()+infixr 0 :->+type family as :-> r where+  (a ': as) :-> r = a -> as :-> r+  '[] :-> r = r++methodsFor :: Name -- ^ Typeclass name+           -> TypeQ -- ^ @ :: [Symbol]@+ +-- | Retrieve the method names of a typeclass as a typelevel list of @Symbol@s.+-- A good default for instantiating the 'Methods' type,+-- which is robust against changing method names+methodsFor n = do+  ClassI (ClassD _ _ _ _ (map sigSym -> ss)) _ <- reify n+  return (typeList ss )+  where sigSym (SigD (nameBase -> s) _) = LitT (StrTyLit s)+

@@ -0,0 +1,8 @@+module Monad.Foo where+import Monad.Impl++data Foo a = Foo a++impl @Monad [t|Foo|]+  ! #return [|Foo|]+  ! #bind [|\(Foo a) f -> f a|]

@@ -0,0 +1,15 @@+module Monad.Impl (module X) where+import Impl as X++instance Impl Monad where+  type Methods Monad = '["return","bind"]+  impl m (Arg return) (Arg bind) = [d|+    instance Monad $m where+      return = $return+      (>>=) = $bind+    instance Applicative $m where +      pure = $return+      mf <*> ma = $bind mf $ \f -> $bind ma $ \a -> $return (f a)+    instance Functor $m where+      fmap f ma = $bind ma $ \a -> $return (f a)+   |]

@@ -0,0 +1,41 @@+cabal-version: 2.2+name: impl+homepage: https://github.com/exordium/impl#readme+version: 0.1.0.0+category: Development, Template Haskell+synopsis: Framework for defaulting superclasses+stability: cursed+bug-reports: https://github.com/exordium/impl/issues+author: Dai+maintainer: daig@sodality.cc+copyright: 2018 Sodality+license: MIT++source-repository head+  type: git+  location: https://github.com/exordium/impl++common x+  default-language: Haskell2010+  default-extensions: TypeFamilies, ViewPatterns, DataKinds, TypeOperators,  AllowAmbiguousTypes, TypeApplications, OverloadedLabels, TemplateHaskell, PolyKinds+  build-depends: base ^>= 4.12.0.0++library+  import: x+  exposed-modules: Impl+  other-modules: Impl.Utils+  build-depends: template-haskell ^>= 2.14.0.0+               , named ^>= 0.2.0.0++Flag DumpExample+  Description: Show generated TH in example+  Default: False+  Manual: True++library example+  import: x+  hs-source-dirs: example+  exposed-modules: Monad.Impl, Monad.Foo+  if flag(DumpExample)+    ghc-options: -ddump-splices -dsuppress-uniques+  build-depends: impl