-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Simple Lexer Creation
--   
--   This package provides the tools to create a simple lexer.
@package hlex
@version 1.0.0


-- | Tools needed to create a <a>Lexer</a> from a lexical <a>Grammar</a>.
module Hlex

-- | Lexical grammar made up of <a>GrammarRule</a>s.
--   
--   The <b>order is important</b>. The <a>Lexer</a> will apply each
--   <a>GrammarRule</a> rule in the order listed.
type Grammar token = [GrammarRule token]

-- | These are the individual rules that make up a <a>Grammar</a>.
--   
--   Takes a <b>POSIX regular expression</b> then converts it to a token or
--   skips it.
data GrammarRule token

-- | Skips over any matches.
Skip :: String -> GrammarRule token

-- | Takes a function that converts the matched string to a token.
Tokenize :: String -> (String -> token) -> GrammarRule token

-- | Converts any regular expression matches to a given token.
JustToken :: String -> token -> GrammarRule token

-- | Returns an error with a message when a match occurs.
Error :: String -> String -> GrammarRule token

-- | Converts a string into a list of tokens. If the string does not follow
--   the Lexer's <a>Grammar</a> a <a>LexException</a> will be returned.
type Lexer token = String -> Either LexException [token]

-- | Exception thrown when a <a>Lexer</a> encounters an error when lexxing
--   a string.
data LexException

-- | Exception thrown when a substring cannot be matched.
UnmatchedException :: Int -> Int -> String -> LexException

-- | Exception thrown when a macth is found on the <a>Error</a>
--   <a>GrammarRule</a>.
MatchedException :: Int -> Int -> String -> String -> LexException

-- | Takes a given <a>Grammar</a> and turns it into a <a>Lexer</a>.
hlex :: Grammar token -> Lexer token
instance GHC.Classes.Eq Hlex.LexException
instance GHC.Show.Show Hlex.LexException
instance GHC.Read.Read Hlex.LexException