Condition.hs

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

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{-# LANGUAGE UndecidableInstances #-}

module Feldspar.Core.Constructs.Condition
    ( module Language.Syntactic.Constructs.Condition
    ) where

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

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

instance Sharable Condition

instance SizeProp (Condition :|| Type)
  where
    sizeProp (C' Condition) (_ :* WrapFull t :* WrapFull f :* Nil)
        = infoSize t \/ infoSize f

instance ( (Condition :|| Type) :<: dom
         , (Logic     :|| Type) :<: dom
         , OptimizeSuper dom
         )
      => Optimize (Condition :|| Type) dom
  where
    constructFeatOpt (C' Condition) (c :* t :* f :* Nil)
        | Just c' <- viewLiteral c = return $ if c' then t else f

    constructFeatOpt (C' Condition) (_ :* t :* f :* Nil)
        | alphaEq t f = return t

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

    constructFeatOpt a args = constructFeatUnOpt a args

    constructFeatUnOpt x@(C' _) = constructFeatUnOptDefault x

      -- TODO Propagate size information from the condition to the branches. For
      --      example
      --
      --        condition (x<10) (min x 20) x  ==>  x