import Language.Haskell.TH.Lib
import Language.Haskell.TH.Ppr
import Language.Haskell.TH.Syntax
-import Prelude hiding ( concat, concatMap, exp
+import Prelude hiding ( concat, concatMap, exp, filter
, foldl, foldr, foldl1, foldr1, null)
import Prelude.Unicode
= return (wrapperTy, deriveUnfoldable)
| classTy ≡ ''Foldable
= return (wrapperTy, deriveFoldable)
+ | classTy ≡ ''Collection
+ = return (wrapperTy, deriveCollection)
+inspectInstance (AppT (AppT (AppT (ConT classTy) wrapperTy) _) _)
+ | classTy ≡ ''Indexed
+ = return (wrapperTy, deriveIndexed)
inspectInstance ty
= fail $ "deriveInstance: unsupported type: " ⧺ pprint ty
= [| isSingleton ∘ $unwrap |]
| otherwise
= fail $ "deriveFoldable: unknown method: " ⧺ pprint name
+
+deriveCollection ∷ Q Cxt → Q Type → Q Exp → Q Exp → Q Dec
+deriveCollection c ty wrap unwrap
+ = do names ← methodNames ''Collection
+ instanceD c ty $ concatMap (pointfreeMethod exp) names
+ where
+ exp ∷ Name → Q Exp
+ exp name
+ | name ≡ 'filter
+ = [| ($wrap ∘) ∘ (∘ $unwrap) ∘ filter |]
+ | otherwise
+ = fail $ "deriveCollection: unknown method: " ⧺ pprint name
+
+deriveIndexed ∷ Q Cxt → Q Type → Q Exp → Q Exp → Q Dec
+deriveIndexed c ty wrap unwrap
+ = do names ← methodNames ''Indexed
+ instanceD c ty $ concatMap (pointfreeMethod exp) names
+ where
+ exp ∷ Name → Q Exp
+ exp name
+ | name ≡ 'index
+ = [| (∘ $unwrap) ∘ index |]
+ | name ≡ 'adjust
+ = [| (($wrap ∘) ∘) ∘ flip flip $unwrap ∘ ((∘) ∘) ∘ adjust |]
+ | name ≡ 'inDomain
+ = [| (∘ $unwrap) ∘ inDomain |]
+ | name ≡ '(//)
+ = [| ($wrap ∘) ∘ (//) ∘ $unwrap |]
+ | name ≡ 'accum
+ = [| (($wrap ∘) ∘) ∘ (∘ $unwrap) ∘ accum |]
+ | otherwise
+ = fail $ "deriveIndexed: unknown method: " ⧺ pprint name