Added a joinWith helper (short for concat . intersperse) and changed most of the uses in the code to use the helper function

checks/ArrayUsageCheck.hs

@@ -232,7 +232,7 @@ formatProblem varToIndex (eq, ineq)
                                        ++ " " ++ op ++ " " ++ show (negate $ item ! 0)
 
         showEq :: Array CoeffIndex Integer -> m String
-        showEq = liftM (concat . intersperse " + ") . mapM showItem . filter ((/= 0) . snd) . tail . assocs
+        showEq = liftM (joinWith " + ") . mapM showItem . filter ((/= 0) . snd) . tail . assocs
 
         showItem :: (CoeffIndex, Integer) -> m String
         showItem (n, a) = case find ((== n) . snd) $ Map.assocs varToIndex of
@@ -255,7 +255,7 @@ solve (ls,vm,(eq,ineq)) = case solveProblem eq ineq of
 formatSolution :: (CSMR m, Monad m) => VarMap -> VariableMapping -> m String
 formatSolution varToIndex vm
  = do names <- mapM valOfVar $ Map.assocs varToIndex
-      return $ concat $ intersperse " , " $ catMaybes names
+      return $ joinWith " , " $ catMaybes names
       where
         indexToVar = flip lookup $ map revPair $ Map.assocs varToIndex
 
@@ -275,7 +275,7 @@ formatSolution varToIndex vm
               -1 -> "-"
               n -> show n ++ "*"
 
-        showWithCoeff xs = liftM (concat . intersperse " + ") $ mapM showWithCoeff' xs
+        showWithCoeff xs = liftM (joinWith " + ") $ mapM showWithCoeff' xs
 
         valOfVar (varExp,k) = case Map.lookup k indexToConst of 
           Nothing -> return Nothing
@@ -290,7 +290,7 @@ formatSolution varToIndex vm
 
         formatBounds _ [] = ""
         formatBounds f [b] = f b
-        formatBounds f bs = f $ "(" ++ concat (intersperse "," bs) ++ ")"
+        formatBounds f bs = f $ "(" ++ joinWith "," bs ++ ")"
 
 showFlattenedExpSet :: Monad m => (A.Expression -> m String) -> Set.Set FlattenedExp -> m String
 showFlattenedExpSet showExp s = liftM concat $ sequence $ intersperse (return " + ") $ map (showFlattenedExp showExp) $ Set.toList s

checks/Check.hs

@@ -446,7 +446,7 @@ showCodeExSet :: (CSMR m, Ord a, ShowOccam a, ShowRain a) => ExSet a -> m String
 showCodeExSet Everything = return "<all-vars>"
 showCodeExSet (NormalSet s)
     = do ss <- mapM showCode (Set.toList s)
-         return $ "{" ++ concat (intersperse ", " ss) ++ "}"
+         return $ "{" ++ joinWith ", " ss ++ "}"
 
 checkInitVarPass :: Pass
 checkInitVarPass = pass "checkInitVar" [] []

common/Utils.hs

@@ -328,7 +328,7 @@ showMaybe showFunc (Just x) = "Just " ++ showFunc x
 showMaybe _ Nothing = "Nothing"
 
 showListCustom :: (a -> String) -> [a] -> String
-showListCustom showFunc list = "[" ++ concat (intersperse "," (map showFunc list)) ++ "]"
+showListCustom showFunc list = "[" ++ joinWith "," (map showFunc list) ++ "]"
 
 showPairCustom :: (a -> String) -> (b -> String) -> (a,b) -> String
 showPairCustom showA showB (a,b) = "(" ++ showA a ++ "," ++ showB b ++ ")"
@@ -398,3 +398,9 @@ liftWrapStateT wrap m
 foldM1 :: Monad m => (a -> a -> m a) -> [a] -> m a
 foldM1 f (x:xs) = foldM f x xs
 foldM1 _ [] = fail "Empty list in foldM1"
+
+-- | A shortcut for concat and intersperse.
+-- For example, @joinWith " " names@ is the same as @concat (intersperse " "
+-- names)@
+joinWith :: [a] -> [[a]] -> [a]
+joinWith x = concat . intersperse x

frontends/ParseOccam.hs

@@ -2004,7 +2004,7 @@ defaultDecl = concat
      [Token emptyMeta $ Pragma $ "TOCKEXTERNAL \""
       ++ showOccam rt
       ++ " FUNCTION \"" ++ concatMap doubleStar op ++ "\"("
-      ++ concat (intersperse "," params)
+      ++ joinWith "," params
       ++ ") = "
       ++ occamDefaultOperator op ts
       ++ "\""

pregen/GenNavAST.hs

@@ -74,7 +74,7 @@ instancesFrom w
     -- left to apply.
     baseInst :: [String]
     baseInst
-        = [ "instance (" ++ concat (intersperse ", " context) ++ ") =>"
+        = [ "instance (" ++ joinWith ", " context ++ ") =>"
           , "         Polyplate m () o0 (" ++ wName ++ ") where"
           ] ++
           (if isAlgType wDType
@@ -116,7 +116,7 @@ instancesFrom w
         ctrName = modPrefix ++ ctrS
         makeCtr vs
             = if isTuple
-                then "(" ++ (concat $ intersperse ", " vs) ++ ")"
+                then "(" ++ joinWith ", " vs ++ ")"
                 else ctrName ++ concatMap (" " ++) vs
         ctrInput = makeCtr ["a" ++ show i | i <- argNums]
         ctrResult = makeCtr ["r" ++ show i | i <- argNums]

pregen/GenOrdAST.hs

@@ -58,7 +58,7 @@ ordFor' typeName x = process $ map processConstr $ dataTypeConstrs $ dataTypeOf
       ++ concat [ [ "  compare (" ++ name ++ headL ++ ") (" ++ name ++ headR ++ ") = " ++
                     --Shortcut:
                     if null comparisons then "EQ" else
-                      "combineCompare [" ++ concat (intersperse "," comparisons) ++ "]"
+                      "combineCompare [" ++ joinWith "," comparisons) ++ "]"
                   ] ++ if isLast then [] else
                   [ "  compare (" ++ name ++ " {}) _ = LT"
                   , "  compare _ (" ++ name ++ " {}) = GT"]

pregen/GenTagAST.hs

@@ -80,7 +80,7 @@ genItem' suffix typeName (num, name, paramTypes)
   where
     typeSuffix = ""
 
-    params = concat $ intersperse " -> " $ paramTypes ++ [typeName]
+    params = joinWith " -> " $ paramTypes ++ [typeName]
 
     n = show num
     mname = "m" ++ name ++ suffix