{- |
Module : ./atermlib/src/ATerm/Diff.hs
Description : compute the differences of two unshared ATerms
Copyright : (c) Klaus Luettich, Uni Bremen 2005
License : GPLv2 or higher, see LICENSE.txt
Maintainer : Christian.Maeder@dfki.de
Stability : provisional
Portability : non-portable (imports ATerm.Unshared)
Provides functions that calculate differences in unshared 'ATerm's.
-}
module ATerm.Diff (atDiff) where
import ATerm.Unshared
import Data.List
{- | all diferences between both terms are replaced by appropiate
placeholders (in @\<\>@) and the differing terms are added to the
list of ATerm as arguments to the function symbol @diff@. -}
--
{- /Note:
this function ignores annotions and the resulting ATerm does not
contain any annotation!/ -}
atDiff :: ATerm -> ATerm -> (ATerm, [ATerm])
atDiff a1@(AAppl s1 atl1 _) a2@(AAppl s2 atl2 _)
| s1 == s2 && atl1 == atl2 = (AAppl s1 atl1 [], [])
| s1 == s2 &&
length atl1 == length atl2 =
case atDiffL atl1 atl2 of
(diffs, atl) -> (AAppl s1 atl [], diffs)
| otherwise = (AAppl "<diff-appls>" [] [], [AAppl "diff" [a1, a2] []])
atDiff a1@(AInt i1 _) a2@(AInt i2 _)
| i1 == i2 = (AInt i1 [], [])
| otherwise = (AAppl "<diff-int>" [] [], [AAppl "diff" [a1, a2] []])
atDiff a1@(AList l1 _) a2@(AList l2 _)
| l1 == l2 = (AList l1 [], [])
| length l1 == length l2 =
case atDiffL l1 l2 of
(diffs, atl) -> (AList atl [], diffs)
| otherwise = (AList [AAppl "<diff-lists>" [] []] [],
[AAppl "diff" [a1, a2] []])
atDiff a1 a2 = (AAppl "<diff-types>" [] [], [AAppl "diff" [a1, a2] []])
atDiffL :: [ATerm] -> [ATerm] -> ([ATerm], [ATerm])
atDiffL atl1 atl2 =
mapAccumL (\ acc (ia1, ia2) ->
case atDiff ia1 ia2 of
(at, diffs) -> (acc ++ diffs, at)) [] (zip atl1 atl2)