Variable parser

gistfile1.hs

-- | A variable
-- x.y[3].z[2][9]
variableParser :: Parser Var
variableParser = do
  pos <- getSourcePos
  var <- parseSimpleVar pos <?> "Simple var"
  go var

  where
    
    go :: Var -> Parser Var
    go var = do
      pos <- getSourcePos
      next <- optional $
              try ( parseFieldVar var pos <?> "field var" ) <|>
              try ( parseSubscriptVar var pos <?> "subscript var" )
      case next of
        Nothing -> return var -- There is nothing more to this var
        Just var' -> go var'  -- There is more, continue parsing

    parseFieldVar :: Var -> SourcePos -> Parser Var
    parseFieldVar var pos = do
      symbol "."
      name <- identifier  
      return $ FieldVar var name pos

    parseSubscriptVar :: Var -> SourcePos -> Parser Var
    parseSubscriptVar var pos = do
      exp <- squareBrackets $ parseExp
      return $ SubscriptVar var exp pos

    parseSimpleVar :: SourcePos -> Parser Var
    parseSimpleVar pos = do
      name <- identifier

      return $ SimpleVar name pos