attempted fixing 6. it didnt work.

cw/src/Challenges.hs

@@ -41,6 +41,11 @@ data LamExpr = LamMacro String | LamApp LamExpr LamExpr  |
 
 -- ADD YOUR OWN CODE HERE
 
+
+{--| The following code is copyright of the University of Southampton |--
+ --| The author of this code is Isaac Klugman                         |--}
+
+
 ------------------------------------------Challenge 1-------------------------------------------------          -- | inline comments
 
 
@@ -271,13 +276,23 @@ macroDef [] = ""
 macroDef ( (name,expr):ms ) = foldl1 (++) ["def ",name," = ",exprToStr [] expr," in ",macroDef ms]
 
 
+-- {--| replaces a macro with its definition             |--}
+-- catchMacroStr :: [(String,LamExpr)] -> LamExpr -> String
+-- catchMacro ms e | macros == [] = exprToStr ms e
+--                 | otherwise    = fst $ head macros
+--     where
+--       macros = filter ( (e==) . snd ) ms
+
 {--| replaces a macro with its definition             |--}
-catchMacro :: [(String,LamExpr)] -> LamExpr -> String
-catchMacro ms e | macros == [] = exprToStr ms e
-                | otherwise    = fst $ head macros
+catchMacroExpr :: [(String,LamExpr)] -> LamExpr -> LamExpr
+catchMacroExpr ms e | macros == [] = e
+                    | otherwise    = LamMacro $ (fst . head) macros
     where
       macros = filter ( (e==) . snd ) ms
 
+catchAndConvert :: [(String,LamExpr)] -> LamExpr -> String
+catchAndConvert ms e = exprToStr ms $ catchMacroExpr ms e
+
 
 {--| converts expr to str                             |--
  --| params:                                          |--
@@ -285,22 +300,26 @@ catchMacro ms e | macros == [] = exprToStr ms e
  --|   -expr to convert                               |--
  --| returns expr in string form                      |--}
 exprToStr :: [(String,LamExpr)] -> LamExpr -> String
-exprToStr ms e@(LamApp e1 e2) | e == eNone  = none
-                              | e == eLeft  = left
-                              | e == eRight = right
-                              | e == eBoth  = both
+exprToStr ms e@(LamApp e1 e2) | eMacros == eNone  = none
+                              | eMacros == eLeft  = left
+                              | eMacros == eRight = right
+                              | eMacros == eBoth  = both
+                              | otherwise    = "fuck"
     where
-      none                   = foldl1 (++) [    catchMacro ms e1, " ", catchMacro ms e2    ]                    -- | applying different uses of parenthese to
-      left                   = foldl1 (++) ["(",catchMacro ms e1,") ", catchMacro ms e2    ]                    -- | determine when they are necessary
-      right                  = foldl1 (++) [    catchMacro ms e1, " (",catchMacro ms e2,")"]
-      both                   = foldl1 (++) ["(",catchMacro ms e1,") (",catchMacro ms e2,")"]
+      eMacros = LamApp (catchMacroExpr ms e1) (catchMacroExpr ms e2)                                            -- | when testing for parentheses, macros will be replaced
+                                                                                                                -- | so macros must be replaced in the original expr
+
+      none                   = foldl1 (++) [    catchAndConvert ms e1, " ", catchAndConvert ms e2    ]          -- | applying different uses of parenthese to
+      left                   = foldl1 (++) ["(",catchAndConvert ms e1,") ", catchAndConvert ms e2    ]          -- | determine when they are necessary
+      right                  = foldl1 (++) [    catchAndConvert ms e1, " (",catchAndConvert ms e2,")"]
+      both                   = foldl1 (++) ["(",catchAndConvert ms e1,") (",catchAndConvert ms e2,")"]
 
       Just (LamDef _ eNone)  = parseLamMacro none
       Just (LamDef _ eLeft)  = parseLamMacro left
       Just (LamDef _ eRight) = parseLamMacro right
       Just (LamDef _ eBoth)  = parseLamMacro both
 
-exprToStr ms (LamAbs   x  e ) = "\\x" ++ show x ++ " -> " ++ catchMacro ms e
+exprToStr ms (LamAbs   x  e ) = "\\x" ++ show x ++ " -> " ++ catchAndConvert ms e
 exprToStr ms (LamVar   x    ) = "x"   ++ show x
 exprToStr ms (LamMacro m    ) = m
 
@@ -569,10 +588,11 @@ redex (LamApp e1 e2)          = redex e1 || redex e2
 
 eval1cbv :: [ (String,LamExpr) ] -> LamExpr -> LamExpr
 eval1cbv ms (LamAbs x e)                           = LamAbs x e
-eval1cbv ms (LamMacro name)                        = (snd . head) $ filter ((name==) . fst) ms
 eval1cbv ms (LamApp (LamAbs x e1) e@(LamAbs y e2)) = subst e1 x e
-eval1cbv ms (LamApp e1@(LamAbs x e) e2)            = LamApp e1 $ eval1cbv ms e2
+eval1cbv ms (LamApp e1@(LamAbs x e) e2)            = LamApp e1 (eval1cbv ms e2)
 eval1cbv ms (LamApp e1 e2)                         = LamApp (eval1cbv ms e1) e2
+eval1cbv ms (LamMacro name)                        = (snd . head) $ filter ((name==) . fst) ms
+eval1cbv ms (LamVar x)                             = LamVar x
 
 
 eval1cbn :: [ (String,LamExpr) ] -> LamExpr -> LamExpr