{- |

Module : $Header$

Description : Abstract syntax for reduce

Copyright : (c) Dominik Dietrich, DFKI Bremen 2010

License : GPLv2 or higher, see LICENSE.txt

Maintainer : dominik.dietrich@dfki.de

Stability : experimental

Portability : portable

this file defines morhpisms for the reduce logic. A morphism is a mapping of operator symbols

-}

module CSL.Morphism

( Morphism (..) -- datatype for Morphisms

, pretty -- pretty printing

, idMor -- identity morphism

, composeMor -- composition

, inclusionMap -- inclusion map

, mapSentence -- map of sentences

, mapSentenceH -- map of sentences, without Result type

, applyMap -- application function for maps

, applyMorphism -- application function for morphism

, morphismUnion

) where

import qualified Data.Map as Map

import qualified Data.Set as Set

import CSL.Sign as Sign

import qualified Common.Result as Result

import CSL.AS_BASIC_CSL

import Common.Id as Id

import Common.Result

import Common.Doc

import Common.DocUtils

-- | The datatype for morphisms in reduce logic as maps of sets

data Morphism = Morphism

{ source :: Sign

, target :: Sign

, operatorMap :: Map.Map Id Id

} deriving (Eq, Ord, Show)

instance Pretty Morphism where

pretty = printMorphism

-- | pretty printer for morphisms

printMorphism :: Morphism -> Doc

printMorphism m = pretty (source m) <> text "-->" <> pretty (target m)

<> vcat (map ( \ (x, y) -> lparen <> pretty x <> text ","

<> pretty y <> rparen) $ Map.assocs $ operatorMap m)

-- | Constructs an id-morphism

idMor :: Sign -> Morphism

idMor a = inclusionMap a a

-- | calculates the composition of two morhpisms f:X->Y, g:Y->Z

composeMor :: Morphism -> Morphism -> Result Morphism

composeMor f g =

let fSource = source f

gTarget = target g

fMap = operatorMap f

gMap = operatorMap g

in return Morphism

{ source = fSource

, target = gTarget

, operatorMap = if Map.null gMap then fMap else

Set.fold ( \ i -> let j = applyMap gMap (applyMap fMap i) in

if i == j then id else Map.insert i j)

Map.empty $ opIds fSource }

-- | constructs the inclusion map for a given signature

inclusionMap :: Sign.Sign -> Sign.Sign -> Morphism

inclusionMap s1 s2 = Morphism

{ source = s1

, target = s2

, operatorMap = Map.empty }

-- | Application function for propMaps

applyMap :: Map.Map Id Id -> Id -> Id

applyMap operatormap idt = Map.findWithDefault idt idt operatormap

-- | Application funtion for morphisms

applyMorphism :: Morphism -> Id -> Id

applyMorphism mor idt = Map.findWithDefault idt idt $ operatorMap mor

-- | sentence translation along signature morphism

-- here just the renaming of formulae

mapSentence :: Morphism -> CMD -> Result.Result CMD

mapSentence mor = return . mapSentenceH mor

mapSentenceH :: Morphism -> CMD -> CMD

mapSentenceH _ frm = frm

morphismUnion :: Morphism -> Morphism -> Result.Result Morphism

morphismUnion mor1 mor2 =

let pmap1 = operatorMap mor1

pmap2 = operatorMap mor2

p1 = source mor1

p2 = source mor2

up1 = Set.difference (opIds p1) $ Map.keysSet pmap1

up2 = Set.difference (opIds p2) $ Map.keysSet pmap2

(pds, pmap) = foldr ( \ (i, j) (ds, m) -> case Map.lookup i m of

Nothing -> (ds, Map.insert i j m)

Just k -> if j == k then (ds, m) else

(Diag Error

("incompatible mapping of prop " ++ showId i " to "

++ showId j " and " ++ showId k "")

nullRange : ds, m)) ([], pmap1)

(Map.toList pmap2 ++ map (\ a -> (a, a))

(Set.toList $ Set.union up1 up2))

in if null pds then return Morphism

{ source = unite p1 p2

, target = unite (target mor1) $ target mor2

, operatorMap = pmap } else Result pds Nothing