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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 TypeCtx)

instance SizeProp (Condition TypeCtx)
  where
    sizeProp cond@Condition (_ :* WrapFull t :* WrapFull f :* Nil)
        | TypeWit <- fromSatWit $ witnessSat cond
        = infoSize t \/ infoSize f

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

    constructFeatOpt Condition (c :* t :* f :* Nil)
        | alphaEq t f = return t

    constructFeatOpt cond@Condition ((op :$ c) :* t :* f :* Nil)
        | Just (_,Not) <- prjDecor op
        = constructFeat cond (c :* f :* t :* Nil)

    constructFeatOpt a args = constructFeatUnOpt a args

    constructFeatUnOpt = constructFeatUnOptDefault

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