MatchTerm: testing conditions on terms, e.g. nodup

src/GF/UseGrammar/MatchTerm.hs

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+----------------------------------------------------------------------
+-- |
+-- Module      : MatchTerm
+-- Maintainer  : AR
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+--
+-- functions for matching with terms. AR 16/3/2006
+-----------------------------------------------------------------------------
+
+module GF.UseGrammar.MatchTerm where
+
+import GF.Data.Operations
+import GF.Data.Zipper
+
+import GF.Grammar.Grammar
+import GF.Grammar.PrGrammar
+import GF.Infra.Ident
+import GF.Grammar.Values
+import GF.Grammar.Macros
+import GF.Grammar.MMacros
+
+import Control.Monad
+import Data.List
+
+-- test if a term has duplicated idents, either any or just atoms
+
+hasDupIdent, hasDupAtom :: Exp -> Bool
+hasDupIdent = (>1) . maximum . map length . group . sort . allConstants True
+hasDupAtom  = (>1) . maximum . map length . group . sort . allConstants False
+
+-- test if a certain ident occurs in term
+
+grepIdent :: Ident -> Exp -> Bool
+grepIdent c = elem c . allConstants True
+
+-- form the list of all constants, optionally ignoring all but atoms
+
+allConstants :: Bool -> Exp -> [Ident]
+allConstants alsoApp = err (const []) snd . flip appSTM [] . collect where
+  collect e = case e of
+    Q _ c  -> add c e
+    QC _ c -> add c e
+    Cn c   -> add c e
+    App f a | not alsoApp -> case f of
+      App g b -> collect b >> collect a 
+      _ -> collect a
+    _ -> composOp collect e
+  add c e = updateSTM (c:) >> return e