context-free-grammar-0.1.1: src/Data/Cfg/Bnf/Token.hs

-- | Bnf tokens
module Data.Cfg.Bnf.Token
  ( Token(..)
  , TokenType(..)
  ) where

-- | Token types
data TokenType
  = ERROR
  | FULL_STOP -- ^ @.@
  | LOWER_IDENTIFIER
    -- ^ an identifier made of lower-case characters possibly
    -- separated by underscores
  | OR -- ^ @|@
  | UPPER_IDENTIFIER
    -- ^ an identifier made of upper-case characters possibly
    -- separated by underscores
  | YIELDS -- ^ @::=@
  deriving (Eq, Show)

-- | Basic Bnf tokens.  They do not contain location information.
data Token =
  Token TokenType
        String
  deriving (Eq, Show)