--
-- Copyright (c) 2009-2011, ERICSSON AB
-- All rights reserved.
-- 
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are met:
-- 
--     * Redistributions of source code must retain the above copyright notice, 
--       this list of conditions and the following disclaimer.
--     * Redistributions in binary form must reproduce the above copyright
--       notice, this list of conditions and the following disclaimer in the
--       documentation and/or other materials provided with the distribution.
--     * Neither the name of the ERICSSON AB nor the names of its contributors
--       may be used to endorse or promote products derived from this software
--       without specific prior written permission.
-- 
-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
-- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
-- DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
-- FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
-- DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
-- SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
-- CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
-- OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--

{-# LANGUAGE UndecidableInstances #-}

module Feldspar.Core.Constructs.Eq
where

import Language.Syntactic
import Language.Syntactic.Interpretation.Semantics
import Language.Syntactic.Constructs.Binding
import Language.Syntactic.Constructs.Literal

import Feldspar.Range
import Feldspar.Core.Types
import Feldspar.Core.Interpretation

data EQ a
  where
    Equal    :: (Type a, Eq a) => EQ (a :-> a :-> Full Bool)
    NotEqual :: (Type a, Eq a) => EQ (a :-> a :-> Full Bool)

instance WitnessCons EQ
  where
    witnessCons Equal    = ConsWit
    witnessCons NotEqual = ConsWit

instance WitnessSat EQ
  where
    type SatContext EQ  = TypeCtx
    witnessSat Equal    = SatWit
    witnessSat NotEqual = SatWit

instance MaybeWitnessSat TypeCtx EQ
  where
    maybeWitnessSat = maybeWitnessSatDefault

instance Semantic EQ
  where
    semantics Equal    = Sem "(==)" (==)
    semantics NotEqual = Sem "(/=)" (/=)

instance ExprEq   EQ where exprEq = exprEqSem; exprHash = exprHashSem
instance Render   EQ where renderPart = renderPartSem
instance ToTree   EQ
instance Eval     EQ where evaluate = evaluateSem
instance EvalBind EQ where evalBindSym = evalBindSymDefault
instance SizeProp EQ where sizeProp = sizePropDefault
instance Sharable EQ

instance AlphaEq dom dom dom env => AlphaEq EQ EQ dom env
  where
    alphaEqSym = alphaEqSymDefault

instance (EQ :<: dom, Optimize dom dom) => Optimize EQ dom
  where
    constructFeatOpt Equal (a :* b :* Nil)
        | alphaEq a b
        = return $ literalDecor True

    constructFeatOpt Equal (a :* b :* Nil)
        | RangeSet ra <- infoRange (getInfo a)
        , RangeSet rb <- infoRange (getInfo b)
        , ra `disjoint` rb
        = return $ literalDecor False

    constructFeatOpt NotEqual (a :* b :* Nil)
        | alphaEq a b
        = return $ literalDecor False

    constructFeatOpt NotEqual (a :* b :* Nil)
        | RangeSet ra <- infoRange (getInfo a)
        , RangeSet rb <- infoRange (getInfo b)
        , ra `disjoint` rb
        = return $ literalDecor True

    constructFeatOpt a args = constructFeatUnOpt a args

    constructFeatUnOpt = constructFeatUnOptDefault