diff --git a/checks/ArrayUsageCheck.hs b/checks/ArrayUsageCheck.hs
index f4686c5..92e1ddf 100644
--- a/checks/ArrayUsageCheck.hs
+++ b/checks/ArrayUsageCheck.hs
@@ -449,7 +449,7 @@ makeEquations accesses bound
         rs' = zip (repeat AARead) rs
         
         makeRepVarEq :: ((A.Name, A.Replicator), Bool) -> StateT VarMap (Either String) (A.Variable, EqualityConstraintEquation, EqualityConstraintEquation)
-        makeRepVarEq ((varName, A.For m from for), _)
+        makeRepVarEq ((varName, A.For m from for _), _)
           = do from' <- makeSingleEq from "replication start"
                upper <- makeSingleEq (A.Dyadic m A.Subtr (A.Dyadic m A.Add for from) (makeConstant m 1)) "replication count"
                return (A.Variable m varName, from', upper)
@@ -470,7 +470,7 @@ makeEquations accesses bound
     -- | Turns all instances of the variable from the given replicator into their primed version in the given expression
     mirrorFlaggedVars :: [FlattenedExp] -> ((A.Name, A.Replicator),Bool) -> StateT [(CoeffIndex,CoeffIndex)] (StateT VarMap (Either String)) [FlattenedExp]
     mirrorFlaggedVars exp (_,False) = return exp
-    mirrorFlaggedVars exp ((varName, A.For m from for), True)
+    mirrorFlaggedVars exp ((varName, A.For m from for _), True)
       = do varIndexes <- lift $ seqPair (varIndex (Scale 1 (A.ExprVariable emptyMeta var,0)), varIndex (Scale 1 (A.ExprVariable emptyMeta var,1)))
            modify (varIndexes :)
            return $ setIndexVar var 1 exp
diff --git a/checks/ArrayUsageCheckTest.hs b/checks/ArrayUsageCheckTest.hs
index af38a00..7fe9701 100644
--- a/checks/ArrayUsageCheckTest.hs
+++ b/checks/ArrayUsageCheckTest.hs
@@ -471,7 +471,7 @@ testMakeEquations = TestLabel "testMakeEquations" $ TestList
     testRep' (ind, problems, (repName, repFrom, repFor), exprs, upperBound) = 
       TestCase $ assertEquivalentProblems ("testMakeEquations " ++ show ind)
         (map (\((a0,a1),b,c,d) -> ((lookup exprs a0, lookup exprs a1), b, makeConsistent c d)) problems)
-          =<< (checkRight $ makeEquations (RepParItem (simpleName "i", A.For emptyMeta repFrom repFor) $
+          =<< (checkRight $ makeEquations (RepParItem (simpleName "i", A.For emptyMeta repFrom repFor (makeConstant emptyMeta 1)) $
             makeParItems [Map.fromList [(UsageCheckUtils.Var $ variable "i",
               [RepBoundsIncl (variable "i") repFrom (subOne $ addExprs repFrom repFor)])]] exprs) upperBound)
   
diff --git a/checks/Check.hs b/checks/Check.hs
index 5ba4579..adfe60f 100644
--- a/checks/Check.hs
+++ b/checks/Check.hs
@@ -124,7 +124,7 @@ addBK mp mp2 g nid n = fmap ((,) $ (map Map.fromList $ productN $ conBK ++
         --TODO only really need consider the connected nodes...
 
         mkBK :: (A.Name, A.Replicator) -> [(Var, [BackgroundKnowledge])]
-        mkBK (n, A.For _ low count) = [(Var v, bk)]
+        mkBK (n, A.For _ low count _) = [(Var v, bk)]
           where
             m = A.nameMeta n
             v = A.Variable m n
diff --git a/checks/UsageCheckUtils.hs b/checks/UsageCheckUtils.hs
index 4fb6027..dc4e164 100644
--- a/checks/UsageCheckUtils.hs
+++ b/checks/UsageCheckUtils.hs
@@ -239,7 +239,8 @@ getVarFormals m = mapUnionVars (getVarFormal m)
     getVarFormal m (A.Formal _ _ n) = processVarW (A.Variable m n) Nothing
 
 getVarRepExp :: A.Replicator -> Vars
-getVarRepExp (A.For _ e0 e1) = getVarExp e0 `unionVars` getVarExp e1
+getVarRepExp (A.For _ e0 e1 e2) = getVarExp e0 `unionVars` getVarExp e1 `unionVars`
+  getVarExp e2
 getVarRepExp (A.ForEach _ e) = getVarExp e
 
 getVarAlternative :: A.Alternative -> Vars
diff --git a/common/ShowCode.hs b/common/ShowCode.hs
index 0db1b37..1686100 100644
--- a/common/ShowCode.hs
+++ b/common/ShowCode.hs
@@ -584,7 +584,8 @@ instance ShowOccam A.Alternative where
          occamOutdent
   
 instance ShowOccam A.Replicator where
-  showOccamM (A.For _ start count) = tell [" = "] >> showOccamM start >> tell [" FOR "] >> showOccamM count
+  showOccamM (A.For _ start count step) = tell [" = "] >> showOccamM start >> tell [" FOR "] >> showOccamM count
+    >> tell [" STEP "] >> showOccamM step
   showOccamM (A.ForEach _ e) = tell [" IN "] >> showOccamM e
 
 instance ShowOccam A.Choice where
@@ -709,7 +710,7 @@ instance ShowRain A.Process where
   showRainM (A.Par _ A.PlacedPar str) = outerRain "placed par" str
 
 instance ShowRain A.Replicator where
-  showRainM (A.For _ start count) = tell [" = "] >> showRainM start >> tell [" for "] >> showRainM count
+  showRainM (A.For _ start count _) = tell [" = "] >> showRainM start >> tell [" for "] >> showRainM count
   showRainM (A.ForEach _ e) = tell ["each ("] >> colon >> showRainM e
 
 --TEMP:
diff --git a/common/TestUtils.hs b/common/TestUtils.hs
index 87b596f..a90885a 100644
--- a/common/TestUtils.hs
+++ b/common/TestUtils.hs
@@ -235,7 +235,8 @@ makePar procList = A.Par emptyMeta A.PlainPar $ A.Several emptyMeta (map (A.Only
 -- | Wraps the given process in a replicated 'A.Par' of the form PAR i = 0 FOR 3.
 makeRepPar :: A.Process -> A.Process
 makeRepPar proc = A.Par emptyMeta A.PlainPar $ A.Spec emptyMeta
-  (A.Specification emptyMeta (simpleName "i") (A.Rep emptyMeta (A.For emptyMeta (intLiteral 0) (intLiteral 3)))) (A.Only emptyMeta proc)
+  (A.Specification emptyMeta (simpleName "i") (A.Rep emptyMeta (A.For emptyMeta (intLiteral 0) (intLiteral 3)
+    (intLiteral 1)))) (A.Only emptyMeta proc)
 
 -- | Creates an assignment to the given 'A.Variable' from the given 'A.Expression.'
 makeAssign :: A.Variable -> A.Expression -> A.Process
diff --git a/common/Types.hs b/common/Types.hs
index 30f1a08..372880b 100644
--- a/common/Types.hs
+++ b/common/Types.hs
@@ -100,7 +100,7 @@ typeOfSpec st
             A.IsChannelArray _ t _ -> return $ Just t
             A.Retypes _ _ t _ -> return $ Just t
             A.RetypesExpr _ _ t _ -> return $ Just t
-            A.Rep _ (A.For _ _ e) -> astTypeOf e >>* Just
+            A.Rep _ (A.For _ _ e _) -> astTypeOf e >>* Just
             A.Rep _ (A.ForEach _ e) -> do t <- astTypeOf e
                                           case t of
                                             A.List t' -> return $ Just t'
@@ -651,7 +651,7 @@ bytesInType _ = return $ BIUnknown
 
 -- | Get the number of items a replicator produces.
 countReplicator :: A.Replicator -> A.Expression
-countReplicator (A.For _ _ count) = count
+countReplicator (A.For _ _ count _) = count
 
 -- | Get the number of items in a Structured as an expression.
 countStructured :: Data a => A.Structured a -> A.Expression
diff --git a/flow/FlowGraphTest.hs b/flow/FlowGraphTest.hs
index e38378c..ff5f717 100644
--- a/flow/FlowGraphTest.hs
+++ b/flow/FlowGraphTest.hs
@@ -84,7 +84,7 @@ sm11 = A.Skip m11
 
 rep :: Data a => Meta -> A.Structured a -> A.Structured a
 rep m = A.Spec mU (A.Specification mU (simpleName "i") (A.Rep m (A.For m undefined
-  undefined)))
+  undefined undefined)))
 
 -- | Shows a graph as a node and edge list.
 showGraph :: (Graph g, Show a, Show b) => g a b -> String
@@ -495,8 +495,8 @@ genElem2 f m = comb2 f (genMeta m)
 genElem3 :: (Meta -> a0 -> a1 -> b) -> Meta -> GenL a0 -> GenL a1 -> GenL b
 genElem3 f m = comb3 f (genMeta m) 
 
---genElem4 :: (Meta -> a0 -> a1 -> a2 -> b) -> Meta -> GenL a0 -> GenL a1 -> GenL a2 -> GenL b
---genElem4 f m = comb4 f (genMeta m) 
+genElem4 :: (Meta -> a0 -> a1 -> a2 -> b) -> Meta -> GenL a0 -> GenL a1 -> GenL a2 -> GenL b
+genElem4 f m = comb4 f (genMeta m) 
 
 -- | A helper function for turning any item that can't be replaced into a GenL form (esp.
 -- for use as a parameter of genElemN).
@@ -525,13 +525,13 @@ comb3 func list0 list1 list2 = (liftM3 (,,)) list0 list1 list2 >>* product3 >>*
     process3 :: ([Meta], a0) -> ([Meta], a1) -> ([Meta],a2) -> ([Meta],b)
     process3 (keys0, val0) (keys1, val1) (keys2, val2) = (keys0++keys1++keys2, func val0 val1 val2)
 
-{-
+
 comb4 :: forall a0 a1 a2 a3 b. (a0 -> a1 -> a2 -> a3 -> b) -> GenL a0 -> GenL a1 -> GenL a2 -> GenL a3 -> GenL b
 comb4 func list0 list1 list2 list3 = (liftM4 (,,,)) list0 list1 list2 list3 >>* product4 >>* map (uncurry4 process4)
   where
     process4 :: ([Meta], a0) -> ([Meta], a1) -> ([Meta],a2) -> ([Meta],a3) -> ([Meta],b)
     process4 (keys0, val0) (keys1, val1) (keys2, val2) (keys3, val3) = (keys0++keys1++keys2++keys3, func val0 val1 val2 val3)
--}
+
 
 -- | Wrapper for Quickcheck.
 -- In order to stop conflict with Quickcheck's in-built rules for things such as pairs
@@ -684,7 +684,7 @@ genOption' :: (Int, Int -> GenL A.Option)
 genOption' = (1, genOption)
 
 genReplicator :: GenL A.Replicator
-genReplicator = nextIdT >>* makeMeta' >>= \m -> genElem3 A.For m genExpression genExpression
+genReplicator = nextIdT >>* makeMeta' >>= \m -> genElem4 A.For m genExpression genExpression genExpression
 
 class ReplicatorAnnotation a where
   replicatorItem :: (Int, Int -> GenL a) -> Maybe (Int, Int -> GenL (A.Structured a))