Binding.hs

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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Imperative.FromCore.Binding where

import Control.Monad.RWS

import Language.Syntactic
import Language.Syntactic.Constructs.Binding.HigherOrder

import Feldspar.Core.Types as Core
import Feldspar.Core.Interpretation
import Feldspar.Core.Constructs.Binding
import qualified Feldspar.Core.Constructs.Binding as Core

import Feldspar.Compiler.Imperative.FromCore.Interpretation

import Feldspar.Compiler.Imperative.Representation (Expression(..))


instance Compile (Core.Variable :|| Type) dom
  where
    compileExprSym (C' (Core.Variable v)) info Nil = do
        env <- ask
        case lookup v (alias env) of
          Nothing -> return $ mkVar (compileTypeRep (infoType info) (infoSize info)) v
          Just e  -> return e

instance Compile (CLambda Type) dom
  where
    compileProgSym = error "Can only compile top-level Lambda"

instance (Compile dom dom, Project (CLambda Type) dom) => Compile Let dom
  where
    compileProgSym Let _ loc (a :* (lam :$ body) :* Nil)
        | Just (SubConstr2 (Lambda v)) <- prjLambda lam
        = do e <- compileLet a (getInfo lam) v
             withAlias v e $ compileProg loc body

    compileExprSym Let _ (a :* (lam :$ body) :* Nil)
        | Just (SubConstr2 (Lambda v)) <- prjLambda lam
        = do e <- compileLet a (getInfo lam) v
             withAlias v e $ compileExpr body

compileLet :: Compile dom dom
           => ASTF (Decor Info dom) a -> Info (a -> b) -> VarId -> CodeWriter (Expression ())
compileLet a info v
    = do
        let ta  = argType $ infoType info
            sa  = infoSize $ getInfo a
            var = mkVar (compileTypeRep ta sa) v
        declare var
        compileProg (Just var) a
        return var

compileBind :: Compile dom dom
            => (VarId, ASTB (Decor Info dom) Type) -> CodeWriter ()
compileBind (v, ASTB e)
     = do
         let info = getInfo e
             var = mkVar (compileTypeRep (infoType info) (infoSize info)) v
         declare var
         compileProg (Just var) e