{-# LANGUAGE FlexibleInstances, FlexibleContexts #-} {- The HList library (C) 2004, Oleg Kiselyov, Ralf Laemmel, Keean Schupke Type-indexed co-products. -} module Data.HList.TIC where import Data.Dynamic import Data.HList.FakePrelude import Data.HList.HListPrelude import Data.HList.HOccurs import Data.HList.TIP {-----------------------------------------------------------------------------} -- A datatype for type-indexed co-products data TIC l = TIC Dynamic {-----------------------------------------------------------------------------} -- Public constructor mkTIC :: ( HTypeIndexed l , HTypeProxied l , HOccurs (Proxy i) l , Typeable i ) => i -> TIC l mkTIC i = TIC (toDyn i) {-----------------------------------------------------------------------------} -- Public destructor unTIC :: ( HTypeIndexed l , HTypeProxied l , HOccurs (Proxy o) l , Typeable o ) => TIC l -> Maybe o unTIC (TIC i) = fromDynamic i {-----------------------------------------------------------------------------} -- A type-indexed type sequence that is a sequence of proxy types class HTypeProxied l instance HTypeProxied HNil instance HTypeProxied l => HTypeProxied (HCons (Proxy e) l) {-----------------------------------------------------------------------------} -- TICs are opaque instance Show (TIC l) where show _ = "" {-----------------------------------------------------------------------------}