Cycles in references now ignored instead of causing an infinite loop.

app/Main.hs

@@ -12,6 +12,7 @@ import Types(Icon(..), Drawing(..), EdgeEnd(..))
 import Translate(translateString)
 
 -- TODO Now --
+-- Fix recursive binds outside of a let.
 -- otherwise Guard special case
 
 -- TODO Later --
@@ -260,7 +261,13 @@ main3 = do
       ]
 
 letTests = [
-  -- TODO: this will cause Translate to loop "y = let x = x in x",
+  "y = let {a = b; b = a; d = f a} in d",
+  "y = let {a = b; b = a} in a",
+  "y = let x = x in x",
+  "y = let {fibs = cons 0 (cons 1 (zipWith (+) fibs (tail fibs)))} in fibs",
+  "fibs = cons 0 (cons 1 (zipWith (+) fibs (tail fibs)))",
+  "y = let x = f x in x",
+  "y = f y",
   "y = let {a = f b; b = g a} in b",
   "y = let {a = 48; b = a + 3} in b",
   "y = let {b = a; a = 84} in f b",
@@ -307,8 +314,8 @@ otherTests = [
   ]
 
 testDecls = mconcat [
-  letTests,
-  otherTests
+  letTests
+  ,otherTests
   ]
 
 translateStringToDrawing :: String -> IO (Diagram B)

app/Translate.hs

@@ -180,12 +180,17 @@ printSelf :: (Show a) => a -> a
 printSelf a = Debug.Trace.trace (show a ++ "\n\n") a
 
 -- | Recursivly find the matching reference in a list of bindings.
--- TODO: Don't infinitly loop here if there is a cycle.
+-- TODO: Might want to present some indication if there is a reference cycle.
 lookupReference :: [(String, Reference)] -> Reference -> Reference
 lookupReference _ ref@(Right p) = ref
-lookupReference bindings ref@(Left s) = case lookup s bindings of
-  Just r -> lookupReference bindings r
-  Nothing -> ref
+lookupReference bindings ref@(Left originalS) = lookupHelper ref where
+  lookupHelper ref@(Right p) = ref
+  lookupHelper ref@(Left s)= case lookup s bindings of
+    Just r -> failIfCycle r $ lookupHelper r
+    Nothing -> ref
+    where
+      failIfCycle r@(Left newStr) res = if newStr == originalS then r else res
+      failIfCycle _ res = res
 
 deleteBindings :: IconGraph -> IconGraph
 deleteBindings (IconGraph a b c d _) = IconGraph a b c d mempty