From d563abb9288d2fe883b68778a0e8ea0d42a1faea Mon Sep 17 00:00:00 2001
From: "John J. Camilleri" <john@digitalgrammars.com>
Date: Sat, 13 Feb 2021 00:59:15 +0100
Subject: [PATCH] Minors

---
 src/compiler/GF/Compile/GrammarToLPGF.hs | 16 +++++++++++-----
 src/runtime/haskell/LPGF.hs              |  2 +-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/compiler/GF/Compile/GrammarToLPGF.hs b/src/compiler/GF/Compile/GrammarToLPGF.hs
index 342cfb098..ed89c7790 100644
--- a/src/compiler/GF/Compile/GrammarToLPGF.hs
+++ b/src/compiler/GF/Compile/GrammarToLPGF.hs
@@ -105,8 +105,8 @@ mkCanon2lpgf opts gr am = do
                     ts <- mapM (go . map (\(C.TableRow (C.RecordPattern rps) lv) -> C.TableRow (C.RecordPattern (tail rps)) lv)) grps
                     return $ L.LFTuple ts
 
-              -- C.TableValue lt trvs | isParamType lt -> do
-              C.TableValue _ trvs -> do
+              C.TableValue lt trvs | isParamType lt -> do
+              -- C.TableValue _ trvs -> do
                 ts <- sequence [ val2lin lv | C.TableRow _ lv <- trvs ] -- TODO variables in lhs ?
                 return $ L.LFTuple ts
 
@@ -129,11 +129,11 @@ mkCanon2lpgf opts gr am = do
                 argIx <- eitherElemIndex (C.VarId v) varIds
                 -- lookup type for function
                 let (C.Abstract _ _ _ funs) = ab
-                (C.Type args _) <- case [ ftype | C.FunDef fid ftype <- funs, fid == funId ] of t:_ -> Right t ; _ -> Left $ printf "Cannot find type for: %s" v
+                (C.Type args _) <- [ ftype | C.FunDef fid ftype <- funs, fid == funId ] `headOrLeft` printf "Cannot find type for: %s" v
                 -- lookup type for argument
                 let C.TypeBinding _ (C.Type _ (C.TypeApp catId _)) = args !! argIx
                 -- lookup label index in argument type
-                rrs <- case [ rrs | C.LincatDef cid (C.RecordType rrs) <- lincats, cid == catId ] of t:_ -> Right t ; _ -> Left $ printf "Cannot find type for: %s" (show catId)
+                rrs <- [ rrs | C.LincatDef cid (C.RecordType rrs) <- lincats, cid == catId ] `headOrLeft` printf "Cannot find type for: %s" (show catId)
                 let rrs' = [ lid | C.RecordRow lid _ <- rrs ]
                 lblIx <- eitherElemIndex lblId rrs'
 
@@ -159,7 +159,6 @@ mkCanon2lpgf opts gr am = do
         L.lins = lins
       })
 
-
 -- | Enumerate all paramvalue combinations for looking up index numbers
 mkParamMap :: [C.ParamDef] -> [[C.LinValue]]
 mkParamMap defs = map mk' defs
@@ -221,6 +220,12 @@ isLFInt :: L.LinFun -> Bool
 isLFInt (L.LFInt _) = True
 isLFInt _ = False
 
+-- | If list is non-empty return its head, else a fallback value
+headOrLeft :: [a] -> b -> Either b a
+headOrLeft (a:_) _ = Right a
+headOrLeft _ b = Left b
+
+
 -- | Convert Maybe to Either value with error
 m2e :: String -> Maybe a -> Either String a
 m2e err = maybe (Left err) Right
@@ -235,6 +240,7 @@ mdi2i (C.ModId i) = mkCId i
 fi2i :: C.FunId -> CId
 fi2i (C.FunId i) = mkCId i
 
+
 -- | Pretty-print canonical grammar, for debugging
 ppCanonical :: C.Grammar -> IO ()
 ppCanonical = putStrLn . render . pp
diff --git a/src/runtime/haskell/LPGF.hs b/src/runtime/haskell/LPGF.hs
index b004ecf44..fd9a78a98 100644
--- a/src/runtime/haskell/LPGF.hs
+++ b/src/runtime/haskell/LPGF.hs
@@ -138,7 +138,7 @@ eval cxt t = case t of
     case (eval cxt t, eval cxt u) of
       (LFTuple vs, LFInt i) -> vs !! (i-1)
       (tp@(LFTuple _), LFTuple is) | all isInt is -> foldl (\(LFTuple vs) (LFInt i) -> vs !! (i-1)) tp is
-      (t',u') -> error $ printf "Incompatible projection:\n%s\n%s" (show t') (show u')
+      (t',u') -> error $ printf "Incompatible projection:\n%s\n%s" (show t) (show u)
   LFArgument i -> cxt !! (i-1)
 
 -- | Turn concrete syntax terms into an actual string