OK

1 files changed, 34 insertions, 12 deletions

diff --git a/src/Parser.hs b/src/Parser.hs
index 611261f..1f768bd 100644
--- a/src/Parser.hs
+++ b/src/Parser.hs
@@ -5,10 +5,18 @@ import           Text.Parsec
 import           Text.Parsec.Language
 import qualified Text.Parsec.Token             as Token
 
+data Error = SyntaxError ParseError | UndeclaredFunction String | InvalidIndex Int | FatalError String
+instance Show Error where
+  show (SyntaxError        err) = show err
+  show (UndeclaredFunction err) = "ERROR: undeclared function " <> show err
+  show (InvalidIndex       err) = "ERROR: invalid index " <> show err
+  show (FatalError         err) = show err
+type Failable = Either Error
+
 languageDef :: GenLanguageDef String u Identity
 languageDef = emptyDef { Token.commentLine     = "#"
                        , Token.identStart      = letter
-                       , Token.identLetter     = alphaNum <|> char '_'
+                       , Token.identLetter     = alphaNum <|> char '?'
                        , Token.reservedOpNames = ["[", "]"]
                        }
 
@@ -26,27 +34,38 @@ reservedOp = Token.reservedOp lexer
 parens :: Parser a -> Parser a
 parens = Token.parens lexer
 
-data Expression = Index Int | Abstraction Int Expression | Application Expression Expression
-  deriving (Ord, Eq)
+data Expression = Bruijn Int | Variable String | Abstraction Expression | Application Expression Expression
+  deriving (Ord, Eq, Show)
 data Instruction = Define String Expression | Evaluate Expression | Comment String
+  deriving (Show)
 
 parseAbstraction :: Parser Expression
 parseAbstraction = do
   reservedOp "["
-  idc <- endBy1 digit spaces
-  build idc <$> parseExpression
- where
-  build (idx : idc) body =
-    Abstraction ((read . pure :: Char -> Int) idx) $ build idc body
-  curry [] body = body
+  exp <- parseExpression
+  reservedOp "]"
+  pure $ Abstraction exp
 
 parseApplication :: Parser Expression
 parseApplication = do
   s <- sepBy1 parseSingleton spaces
   pure $ foldl1 Application s
 
+parseBruijn :: Parser Expression
+parseBruijn = do
+  idx <- digit
+  spaces
+  pure $ Bruijn $ (read . pure) idx
+
+parseVariable :: Parser Expression
+parseVariable = do
+  var <- identifier
+  spaces
+  pure $ Variable var
+
 parseSingleton :: Parser Expression
-parseSingleton = parseAbstraction <|> parens parseApplication
+parseSingleton =
+  parseAbstraction <|> parens parseApplication <|> parseBruijn <|> parseVariable
 
 parseExpression :: Parser Expression
 parseExpression = do
@@ -56,11 +75,14 @@ parseExpression = do
 parseDefine :: Parser Instruction
 parseDefine = do
   var <- identifier
-  space
+  spaces
   Define var <$> parseExpression
 
+parseComment :: Parser Instruction
+parseComment = string "#" >> Comment <$> many letter
+
 parseLine :: Parser Instruction
-parseLine = try parseDefine
+parseLine = try parseDefine <|> parseComment
 
 parseReplLine :: Parser Expression
 parseReplLine = try parseExpression