TemplateHaskell
, UnicodeSyntax
#-}
--- |FIXME: doc
+-- |Doesn't anyone know why these instances can't be derived using
+-- GeneralizedNewtypeDeriving? I think its limitation isn't reasonable
+-- at all...
module Data.Collections.Newtype.TH
( derive
)
type Deriver = Q Cxt → Q Type → Q Exp → Q Exp → Q Dec
--- |FIXME: doc
+-- |Automatic newtype instance deriver for type classes defined by the
+-- collections-api package.
+--
+-- @
+-- {-\# LANGUAGE TemplateHaskell \#-}
+-- module Foo (T) where
+-- import "Data.Collections"
+-- import "Data.Collections.BaseInstances" ()
+-- import qualified Data.Collections.Newtype.TH as C
+-- import qualified "Data.Map" as M
+--
+-- newtype T = T (M.Map 'Int' 'Bool')
+--
+-- C.derive [d| instance 'Unfoldable' T ('Int', 'Bool')
+-- instance 'Foldable' T ('Int', 'Bool')
+-- instance 'Indexed' T 'Int' 'Bool'
+-- ...
+-- |]
+-- @
+--
+-- This function can derive the following instances:
+--
+-- * 'Unfoldable'
+--
+-- * 'Foldable'
+--
+-- * 'Collection'
+--
+-- * 'Indexed'
+--
+-- * 'Map'
+--
+-- * 'Set'
+--
+-- * 'SortingCollection'
+--
derive ∷ Q [Dec] → Q [Dec]
derive = (concat <$>) ∘ (mapM go =≪)
where