Old TODO

This was the contents of the old TODO file. We should triage these at some point and put in their own issues.
```
* happyError should take the current token as an argument in %lexer mode;
it's silly not to, because it means the monad has to keep track of the
previous token in order to report it in the error message.

* BUG in error handling without %lexer: see tests/ParGF.y

* allow polymorphic type signatures for productions.
* allow omitted semnatic values, defaulting to $1?

* unlit properly

* maintain indentation in code between { } so that layout works.

-OLD-------------------------------------------------------------------------

1. Add in a simple lexical analyser

2. Add in choice for lexical analyis

%lexerstyle original -- the default
%lexerstyle auto
%lexerstyle monadic

---[1] :: [Token] -> a ---------------------------------------------------------

As things are now :-(

---[2] :: String -> a ----------------------------------------------------------

Using the special lexer, as defined using

%macro letter ( [A-Z][a-z] )
%autotoken
id ( {letter}({digit}|{letter}) )

---[3] :: ParseM Token -> ParseM a ---------------------------------------------

This presumes the exsitance of the defintions:

type ParseM a b c = a -> ParseR a b
data ParseR a b c = ParseSucc a b | ParseFail c
thenPM :: a -> ParseM a b c
returnPM :: ParseM a b c -> (a -> ParseM d b c) -> ParseM d b c ->

and is intended for *serious* parsers, like our Haskell parser.

You need to give a %eof

-----------------------------------------------------------------------------

******************************************************************************

ToAdd:

--magic-name Sad

allows other names to be used as the *Magic* name, currently
only Happy.
```