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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverlappingInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Imperative.Plugin.Free where

import Feldspar.Compiler.Imperative.Frontend (toInterface, fromInterface, isArray, freeArray)
import Feldspar.Transformation

data Free = Free

instance Transformation Free
  where
    type From Free     = ()
    type To Free       = ()
    type Down Free     = ()
    type Up Free       = ()
    type State Free    = ()

instance Plugin Free
  where
    type ExternalInfo Free = ()
    executePlugin _ _ = result . transform Free () ()

instance Transformable Free Block where
    transform _ _ _ (Block locs b _) = Result bl' () ()
      where
        arrays = filter (isArray . typeof) $ map (toInterface . declVar) locs
        newBody = Sequence (b : map (fromInterface . freeArray) arrays) () ()
        bl' = Block locs newBody ()