GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/GF/Grammar/PatternMatch.hs

@@ -0,0 +1,155 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : PatternMatch
+-- Maintainer  : AR
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/10/12 12:38:29 $ 
+-- > CVS $Author: aarne $
+-- > CVS $Revision: 1.7 $
+--
+-- pattern matching for both concrete and abstract syntax. AR -- 16\/6\/2003
+-----------------------------------------------------------------------------
+
+module GF.Grammar.PatternMatch (matchPattern,
+		     testOvershadow, 
+		     findMatch
+		    ) where
+
+import GF.Data.Operations
+import GF.Grammar.Grammar
+import GF.Infra.Ident
+import GF.Grammar.Macros
+import GF.Grammar.PrGrammar
+
+import Data.List
+import Control.Monad
+
+
+matchPattern :: [(Patt,Term)] -> Term -> Err (Term, Substitution)
+matchPattern pts term = 
+  if not (isInConstantForm term)
+    then prtBad "variables occur in" term
+  else 
+    errIn ("trying patterns" +++ unwords (intersperse "," (map (prt . fst) pts))) $
+    findMatch [([p],t) | (p,t) <- pts] [term]
+
+testOvershadow :: [Patt] -> [Term] -> Err [Patt]
+testOvershadow pts vs = do
+  let numpts = zip pts [0..]
+  let cases  = [(p,EInt i) | (p,i) <- numpts]
+  ts <- mapM (liftM fst . matchPattern cases) vs
+  return $ [p | (p,i) <- numpts, notElem i [i | EInt i <- ts] ]
+
+findMatch :: [([Patt],Term)] -> [Term] -> Err (Term, Substitution)
+findMatch cases terms = case cases of
+   [] -> Bad $"no applicable case for" +++ unwords (intersperse "," (map prt terms))
+   (patts,_):_ | length patts /= length terms -> 
+       Bad ("wrong number of args for patterns :" +++ 
+            unwords (map prt patts) +++ "cannot take" +++ unwords (map prt terms))
+   (patts,val):cc -> case mapM tryMatch (zip patts terms) of
+       Ok substs -> return (val, concat substs)
+       _         -> findMatch cc terms
+
+tryMatch :: (Patt, Term) -> Err [(Ident, Term)]
+tryMatch (p,t) = do 
+  t' <- termForm t
+  trym p t'
+ where
+  isInConstantFormt = True -- tested already
+  trym p t' =
+    case (p,t') of
+      (PVal _ i, (_,Val _ j,_)) 
+          | i == j -> return []
+          | otherwise -> Bad $ "no match of values"
+      (_,(x,Empty,y)) -> trym p (x,K [],y)   -- because "" = [""] = []
+      (PV IW, _) | isInConstantFormt -> return [] -- optimization with wildcard
+      (PV x,  _) | isInConstantFormt -> return [(x,t)]
+      (PString s, ([],K i,[])) | s==i -> return []
+      (PInt s, ([],EInt i,[])) | s==i -> return []
+      (PFloat s,([],EFloat i,[])) | s==i -> return [] --- rounding?
+      (PC p pp, ([], Con f, tt)) | 
+            p `eqStrIdent` f && length pp == length tt ->
+         do matches <- mapM tryMatch (zip pp tt)
+            return (concat matches)
+
+      (PP q p pp, ([], QC r f, tt)) | 
+            -- q `eqStrIdent` r &&  --- not for inherited AR 10/10/2005
+            p `eqStrIdent` f && length pp == length tt ->
+         do matches <- mapM tryMatch (zip pp tt)
+            return (concat matches)
+      ---- hack for AppPredef bug
+      (PP q p pp, ([], Q r f, tt)) | 
+            -- q `eqStrIdent` r && --- 
+            p `eqStrIdent` f && length pp == length tt ->
+         do matches <- mapM tryMatch (zip pp tt)
+            return (concat matches)
+
+      (PR r, ([],R r',[])) |
+            all (`elem` map fst r') (map fst r) ->
+         do matches <- mapM tryMatch 
+                            [(p,snd a) | (l,p) <- r, let Just a = lookup l r']
+            return (concat matches)
+      (PT _ p',_) -> trym p' t'
+      (_, ([],Alias _ _ d,[])) -> tryMatch (p,d)
+
+--      (PP (IC "Predef") (IC "CC") [p1,p2], ([],K s, [])) -> do
+
+      (PAs x p',_) -> do
+         subst <- trym p' t'
+         return $ (x,t) : subst
+
+      (PAlt p1 p2,_) -> checks [trym p1 t', trym p2 t']
+
+      (PNeg p',_) -> case tryMatch (p',t) of
+        Bad _ -> return []
+        _ -> prtBad "no match with negative pattern" p
+
+      (PSeq p1 p2, ([],K s, [])) -> do
+         let cuts = [splitAt n s | n <- [0 .. length s]] 
+         matches <- checks [mapM tryMatch [(p1,K s1),(p2,K s2)] | (s1,s2) <- cuts]
+         return (concat matches)
+
+      (PRep p1, ([],K s, [])) -> checks [
+         trym (foldr (const (PSeq p1)) (PString "") 
+           [1..n]) t' | n <- [0 .. length s]
+        ] >>
+        return []
+
+      (PChar,  ([],K [_], [])) -> return []
+      (PChars cs, ([],K [c], [])) | elem c cs -> return []
+
+      _ -> prtBad "no match in case expr for" t
+  
+isInConstantForm :: Term -> Bool
+isInConstantForm trm = case trm of
+    Cn _     -> True
+    Con _    -> True
+    Q _ _    -> True
+    QC _ _   -> True
+    Abs _ _  -> True
+    App c a  -> isInConstantForm c && isInConstantForm a
+    R r      -> all (isInConstantForm . snd . snd) r
+    K _      -> True
+    Empty    -> True
+    Alias _ _ t -> isInConstantForm t
+    EInt _   -> True
+    _       -> False ---- isInArgVarForm trm
+
+varsOfPatt :: Patt -> [Ident]
+varsOfPatt p = case p of
+  PV x -> [x | not (isWildIdent x)]
+  PC _ ps -> concat $ map varsOfPatt ps
+  PP _ _ ps -> concat $ map varsOfPatt ps
+  PR r    -> concat $ map (varsOfPatt . snd) r
+  PT _ q -> varsOfPatt q
+  _ -> []
+
+-- | to search matching parameter combinations in tables
+isMatchingForms :: [Patt] -> [Term] -> Bool
+isMatchingForms ps ts = all match (zip ps ts') where
+  match (PC c cs, (Cn d, ds)) = c == d && isMatchingForms cs ds
+  match _ = True
+  ts' = map appForm ts
+