0.2.0

Includes better error handling, additional tests, parsing and lexing
fixes to match the desired behavior defined by the new tests, and a very
basic REPL implementation.

src/Research.hs

@@ -24,8 +24,8 @@ reduce expr =
 
 step :: T -> T
 step (Fork left right) = reduce (apply (reduce left) (reduce right))
-step (Stem inner) = Stem (reduce inner) 
-step t = t 
+step (Stem inner) = Stem (reduce inner)
+step t = t
 
 -- SKI Combinators
 _S :: T
@@ -54,20 +54,20 @@ toString str = toList (map toNumber (map fromEnum str))
 ofString :: T -> String
 ofString tc = map (toEnum . ofNumber) (ofList tc)
 
-toNumber :: Int -> T 
+toNumber :: Int -> T
 toNumber 0 = Leaf
 toNumber n =
   Fork
     (if odd n then Stem Leaf else Leaf)
-    (toNumber (n `div` 2)) 
+    (toNumber (n `div` 2))
 
 ofNumber :: T -> Int
 ofNumber Leaf = 0
 ofNumber (Fork Leaf rest) = 2 * ofNumber rest
 ofNumber (Fork (Stem Leaf) rest) = 1 + 2 * ofNumber rest
-ofNumber _ = error "Invalid Tree Calculus number" 
+ofNumber _ = error "Invalid Tree Calculus number"
 
-toList :: [T] -> T 
+toList :: [T] -> T
 toList [] = Leaf
 toList (x:xs) = Fork x (toList xs)
 
@@ -92,13 +92,13 @@ toAscii tree = go tree "" True
         ++ go right (prefix ++ (if isLast then "    " else "|   ")) True
 
 rules :: IO ()
-rules = putStr $ header 
-              ++ (unlines $ tcRules) 
+rules = putStr $ header
+              ++ (unlines $ tcRules)
               ++ (unlines $ haskellRules)
               ++ footer
   where
     tcRules :: [String]
-    tcRules = 
+    tcRules =
       [ "|                                                                               |"
       , "|                  ┌--------- | Tree Calculus | ---------┐                      |"
       , "|                  | 1.  t  t      a b       -> a        |                      |"