Use a Set instead of a list for lambda enclosed nodes.

app/Rendering.hs

@@ -23,6 +23,7 @@ import qualified Data.GraphViz as GV
 import qualified Data.GraphViz.Attributes.Complete as GVA
 import qualified Data.IntMap as IM
 import qualified Data.Map as Map
+import qualified Data.Set as Set
 
 import Control.Arrow(first)
 import Data.Function(on)
@@ -393,7 +394,7 @@ drawLambdaRegions :: forall b . SpecialBackend b Double =>
   -> [(NamedIcon, SpecialQDiagram b Double)]
   -> SpecialQDiagram b Double
 drawLambdaRegions iconInfo placedNodes
-  = mconcat $ fmap (drawRegion [] . fst) placedNodes
+  = mconcat $ fmap (drawRegion Set.empty . fst) placedNodes
   where
     findDia :: NodeName -> SpecialQDiagram b Double
     findDia n1
@@ -401,13 +402,13 @@ drawLambdaRegions iconInfo placedNodes
         (find (\(Named n2 _, _) -> n1 == n2) placedNodes)
 
     -- Also draw the region around the icon the lambda is in.
-    drawRegion :: [NodeName] -> NamedIcon -> SpecialQDiagram b Double
+    drawRegion :: Set.Set NodeName -> NamedIcon -> SpecialQDiagram b Double
     drawRegion parentNames icon = case icon of
       Named _ (LambdaIcon _ _ enclosedNames)
-        -> regionRect $ fmap findDia (parentNames <> enclosedNames)
+        -> regionRect $ findDia <$> Set.toList (parentNames <> enclosedNames)
       Named parentName (NestedApply _ headIcon icons)
         -> mconcat
-           $ drawRegion (parentName:parentNames)
+           $ drawRegion (Set.insert parentName parentNames)
            <$> mapMaybe
            (fmap (findIconFromName iconInfo))
            (headIcon:icons)

app/Translate.hs

@@ -14,6 +14,7 @@ import Data.Either(partitionEithers)
 import qualified Data.Graph.Inductive.PatriciaTree as FGR
 import Data.List(unzip5, partition, intercalate)
 import Data.Maybe(fromMaybe, mapMaybe)
+import qualified Data.Set as Set
 
 import qualified Language.Haskell.Exts as Exts
 import qualified Language.Haskell.Exts.Pretty as PExts
@@ -536,7 +537,7 @@ evalLambda _ context patterns expr = do
   GraphAndRef rhsRawGraph rhsRef <- evalExp rhsContext expr
   let
     paramNames = fmap patternName patternValsWithAsNames
-    enclosedNodeNames = naName <$> sgNodes combinedGraph
+    enclosedNodeNames = Set.fromList $ naName <$> sgNodes combinedGraph
     lambdaNode = FunctionDefNode paramNames enclosedNodeNames
     lambdaPorts = map (nameAndPort lambdaName) $ argumentPorts lambdaNode
     patternGraph = mconcat $ fmap graphAndRefToGraph patternVals

app/TranslateCore.hs

@@ -321,12 +321,12 @@ nestedApplySyntaxNodeToIcon flavor numArgs args =
 
 nestedLambdaToIcon :: [String]  -- labels
                    -> Set.Set (NodeName, Edge)  -- embedded icons
-                   -> [NodeName]  -- body nodes
+                   -> Set.Set NodeName  -- body nodes
                    -> Icon
 nestedLambdaToIcon labels embeddedNodes =
   LambdaIcon labels embeddedBodyNode
   where
-    dummyNode = FunctionDefNode [] []
+    dummyNode = FunctionDefNode [] Set.empty
     embeddedBodyNode = makeArg embeddedNodes (inputPort dummyNode)
 
 nestedCaseOrMultiIfNodeToIcon ::

app/Types.hs

@@ -69,7 +69,7 @@ data Icon = TextBoxIcon String
   | LambdaIcon
     [String]  -- Parameter labels
     (Maybe NodeName)  -- Function body expression
-    [NodeName]  -- Nodes inside the lambda
+    (Set NodeName)  -- Nodes inside the lambda
   | CaseIcon Int
   | CaseResultIcon
   | BindTextBoxIcon String
@@ -114,7 +114,7 @@ data SyntaxNode =
   | LiteralNode String -- Literal values like the string "Hello World"
   | FunctionDefNode  -- Function definition (ie. lambda expression)
     [String]  -- Parameter labels
-    [NodeName]  -- Nodes inside the lambda
+    (Set NodeName)  -- Nodes inside the lambda
   | CaseResultNode -- TODO remove caseResultNode
   | CaseOrMultiIfNode CaseOrMultiIfTag Int
   deriving (Show, Eq, Ord)

test/VisualRenderingTests.hs

@@ -4,6 +4,7 @@ module VisualRenderingTests (
   renderTests
   ) where
 import qualified Diagrams.Prelude as Dia
+import qualified Data.Set as Set
 
 import Rendering (renderDrawing)
 import Types (Labeled(..), NodeName(..), Drawing(..), Edge, Icon(..), Port(..)
@@ -122,7 +123,7 @@ lambdaDia :: Drawing
 lambdaDia = Drawing icons []
   where
     icons = [
-      ni0 $ LambdaIcon ["foo", "bar"] Nothing [n0, n1]
+      ni0 $ LambdaIcon ["foo", "bar"] Nothing (Set.fromList [n0, n1])
       , ni1 CaseResultIcon
       , ni2 $ MultiIfIcon 3
       ]