Initial ternary representation options

Both parsing and conversion from T to ternary representation supported

src/Lexer.hs

@@ -104,7 +104,6 @@ tricuLexer = do
         , closeBracket
         ]
 
-
 lexTricu :: String -> [LToken]
 lexTricu input = case runParser tricuLexer "" input of
   Left err -> error $ "Lexical error:\n" ++ errorBundlePretty err

src/Main.hs

@@ -40,7 +40,7 @@ main = do
     Repl -> do
       putStrLn "Welcome to the tricu REPL"
       putStrLn "You can exit with `CTRL+D` or the `:_exit` command.`"
-      repl Map.empty
+      repl library
     Compile filePath -> do
       result <- evaluateFile filePath
       print result

src/Parser.hs

@@ -11,7 +11,8 @@ import Text.Megaparsec.Error (errorBundlePretty, ParseErrorBundle)
 
 import qualified Data.Set as Set
 
-type Parser = Parsec Void [LToken]
+type Parser    = Parsec Void [LToken]
+type AltParser = Parsec Void String
 
 data TricuAST
   = SVar String
@@ -242,6 +243,42 @@ isLiteral _ = False
 isNewline (LNewline) = True
 isNewline _ = False
 
+-- Alternative parsers
+altSC :: AltParser ()
+altSC = skipMany (char ' ' <|> char '\t' <|> char '\n')
+
+parseTernaryTerm :: AltParser TricuAST
+parseTernaryTerm = do
+  altSC
+  term <- choice parseTernaryTerm'
+  altSC
+  pure term
+  where
+    parseTernaryTerm' =
+      [ try (between (char '(') (char ')') parseTernaryTerm)
+      , try parseTernaryLeaf
+      , try parseTernaryStem
+      , try parseTernaryFork
+      ]
+
+parseTernaryLeaf :: AltParser TricuAST
+parseTernaryLeaf = char '0' *> pure TLeaf
+
+parseTernaryStem :: AltParser TricuAST
+parseTernaryStem = char '1' *> (TStem <$> parseTernaryTerm)
+
+parseTernaryFork :: AltParser TricuAST
+parseTernaryFork = do
+  char '2'
+  term1 <- parseTernaryTerm
+  term2 <- parseTernaryTerm
+  pure $ TFork term1 term2
+
+parseTernary :: String -> Either String TricuAST
+parseTernary input = case runParser (parseTernaryTerm <* eof) "" input of
+  Left err -> Left (errorBundlePretty err)
+  Right ast -> Right ast
+
 -- Error Handling
 handleParseError :: ParseErrorBundle [LToken] Void -> String
 handleParseError bundle =

src/Research.hs

@@ -88,6 +88,12 @@ toList (Fork x rest) = case toList rest of
   Left err -> Left err
 toList _ = Left "Invalid Tree Calculus list"
 
+-- Outputs
+toTernaryString :: T -> String
+toTernaryString Leaf = "0"
+toTernaryString (Stem t) = "1" ++ toTernaryString t
+toTernaryString (Fork t1 t2) = "2" ++ toTernaryString t1 ++ toTernaryString t2
+
 -- Utility
 type Env = Map.Map String T