[Ur] Parsing text files

[Benjamin Barenblat]

On Monday, September 17, 2018, at  4:11 PM EDT, Fabrice Leal wrote:
> I wanted to parse a text file with a non trivial syntax (
> https://en.wikipedia.org/wiki/Portable_Game_Notation) and was wondering
> what would be the best way to achieve this. The best option seems to be
> maybe FFI with C or haskell ... would it be too crazy to do this with plain
> urweb?

I experimented a bit with reimplementing Parsec
(https://hackage.haskell.org/package/parsec) in Ur. The basic idea isn't
too complex - you build a monad that hangs on to four continuations (one
for each of {"parse succeeded", "parse failed"} x {"consumed input",
"consumed no input"}), and it's pretty easy to implement all the
combinators you want in terms of it. I implemented a few combinators
before I realized I really only needed regexes, so I switched to that
(https://git.benjamin.barenblat.name/urweb-regex/).

Anyway, point is, a pure Ur implementation should work, and you should
consider using my regex library for any regular-language bits. :) I
haven't pushed to it in a few years, but it does still build and work. I
actually have some pending changes to it that I'm hoping to push soon -
I'm getting rid of the Boost dependency and making the Autoconf a bit
more robust. Let me know if you're interested in those changes; I can
try to hurry them up.