[Haskell-cafe] Re: Proving my point

[Philippa Cowderoy]

On Sat, 17 May 2008, Achim Schneider wrote:

> There's at least one token before any recursion, so I guess not. After
> all, it terminates. It's my state that does not succeed in directing
> the parser not to mess up, so I'm reimplementing the thing as a
> two-pass but stateless parser now.

In most cases, you're better off stateless unless you've got a really good 
reason for it. Or at least, not using the state for anything that affects 
the parse itself.

> Definitely the easier and clearer
> thing to do: I can have an end of line token that carries the number of
> trailing spaces, so I got perfect indent information without any pain
> involved, at all, and don't have to make parsers fail based on state.
> 

Definitely! Are you doing some form of layout? It's certainly not worth 
doing in one pass IMO, I ended up with a three pass design much like that 
in the Haskell 98 report. Well, that's an understatement - I took the 
algorithm from it! 

-- 
flippa at flippac.org

There is no magic bullet. There are, however, plenty of bullets that
magically home in on feet when not used in exactly the right circumstances.