import Data.Char

data Bracket = Round | Curly | Square deriving Show

data Token = StringLit String
           | Number String
           | Open Bracket
           | Close Bracket
           | DoubleQuote
           | Comma
           | Other String
  deriving Show

lexer :: String -> [Token]
lexer (c:cs)
  | isAlpha c = let (other, rest) = lexOther (c:cs) in Other other : lexer rest
  | c == '"'  = let (sLit, rest) = lexStringLit cs in StringLit sLit : lexer rest
  | isDigit c = let (num, rest) = lexNum (c:cs) in Number num : lexer rest
  | c == '('  = Open Round : lexer cs
  | c == '{'  = Open Curly : lexer cs
  | c == '['  = Open Square : lexer cs
  | c == ')'  = Close Round : lexer cs
  | c == '}'  = Close Curly : lexer cs
  | c == ']'  = Close Square : lexer cs
  | c == ','  = Comma : lexer cs
  | otherwise = lexer cs

lexStringLit :: String -> (String, String)
lexStringLit [] = ("", "")
lexStringLit ('"':rest) = ("", rest)
lexStringLit (c:cs)   = (c:cs', rest)
  where (cs', rest) = lexStringLit cs

lexNum :: String -> (String, String)
lexNum [] = ("", "")
lexNum (c:cs)
  | isDigit c = let (cs', rest) = lexNum cs in (c:cs', rest)
  | otherwise = ("", cs)

lexOther :: String -> (String, String)
lexOther [] = ("", "")
lexOther (c:cs)
  | isAlphaNum c = let (cs', rest) = lexOther cs in (c:cs', rest)
  | otherwise = ("", cs)

main = print . lexer $ '"': repeat 'a'