ConditionM.hs

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

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module Feldspar.Core.Constructs.ConditionM
    ( ConditionM (..)
    ) where

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

import Feldspar.Core.Types
import Feldspar.Core.Interpretation
import Feldspar.Core.Constructs.Logic

data ConditionM m a
  where
    ConditionM :: (Monad m, Type a) =>
                  ConditionM m (Bool :-> m a :-> m a :-> Full (m a))

instance Semantic (ConditionM m)
  where
    semantics ConditionM = Sem "if" ifM
      where
        ifM cond e t = if cond then e else t

instance Equality   (ConditionM m) where equal = equalDefault; exprHash = exprHashDefault
instance Render     (ConditionM m) where renderSym  = renderSymDefault
                                         renderArgs = renderArgsDefault
instance StringTree (ConditionM m)
instance Eval       (ConditionM m) where evaluate = evaluateDefault
instance EvalBind   (ConditionM m) where evalBindSym = evalBindSymDefault
instance Sharable   (ConditionM m)
instance Monotonic  (ConditionM m)

instance AlphaEq dom dom dom env =>
    AlphaEq (ConditionM m) (ConditionM m) dom env
  where
    alphaEqSym = alphaEqSymDefault

instance LatticeSize1 m => SizeProp (ConditionM m)
  where
    sizeProp ConditionM (_ :* WrapFull t :* WrapFull f :* Nil) =
        mergeSize t (infoSize t) (infoSize f)

instance ( ConditionM m :<: dom
         , (Logic :|| Type) :<: dom
         , OptimizeSuper dom
         , LatticeSize1 m
         )
      => Optimize (ConditionM m) dom
  where
    constructFeatOpt _ ConditionM (c :* t :* f :* Nil)
        | Just cl <- viewLiteral c = return $ if cl then t else f

    constructFeatOpt _ ConditionM (_ :* t :* f :* Nil)
        | alphaEq t f = return t

    constructFeatOpt opts cond@ConditionM ((op :$ c) :* t :* f :* Nil)
        | Just (C' Not) <- prjF op
        = constructFeat opts cond (c :* f :* t :* Nil)

    constructFeatOpt opts a args = constructFeatUnOpt opts a args

    constructFeatUnOpt opts ConditionM args@(_ :* t :* _ :* Nil)
        | Info {infoType = tType} <- getInfo t
        = constructFeatUnOptDefaultTyp opts tType ConditionM args