FastParse: small, fast, easy to use parser combinators in Scala

[Haoyi Li]

I just published http://lihaoyi.github.io/fastparse, which is a parser combinator library that is:

- Fast (1/10 to 1/5 the speed of hand-written, v.s. 1/500 of scala-parser-combinators)

- Easy to use (no magic macros, standard method names e.g. map/flatMap, small set of symbolic operators)

- Completely standalone (no heavy dependencies e.g. parboiled2 depending on Shapeless) and <1000LOC

- Runs on both Scala-JVM and Scala.js

It comes with built-in example parsers for simple arithmetic, JSON, and Scala (which naturally contains a parser for XML too!)

If you've ever looked at scala-parser-combinators and found it lacking, or looked at Parboiled2 and found it hard to use, give FastParse a try ^_^

[Alvaro Carrasco]

Wow. Looks great. Will try it out.

Alvaro

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[Alec Zorab]

Haoyi,

Thanks for this, it's a great library and a please to use. However. I'm getting some slightlyodd types come out of the ~ operator - see (https://gist.github.com/AlecZorab/e9b4360c033bbdae75f9) for an example. Is this expected or should I file a bug?

Regards,

Alec

[Haoyi Li]

lol, I knew someone would bump into that, I didn't know it would be this soon! That's a consequence of the tuple extenders only going up to 8

https://github.com/lihaoyi/fastparse/blob/master/fastparse/shared/src/main/scala/fastparse/Implicits.scala#L26-L32

Perhaps you could send a PR to make them longer? Or even make it code-generated...

Someday we'll have HLists, but for now duplicating this for every arity is the easiest thing to do

[Alec Zorab]

I'll have a look.

[Rüdiger Klaehn]

This looks very good. Looks like a good replacement replacement for
parser-combinators.

The documentation does not say anything about thread safety. And it is
using mutable state under the hood. So is the high level API
thread-safe?

Cheers,

Rüdiger

[Haoyi Li]

It's totally thread safe. Mutation is limited to every `parse` call, or during parser initialization. Once you get a Parser[T] back from the constructor, it's frozen and ready to use

[William Harvey]

Amazing work (again...) Haoyi!  Thank you very much for sharing this with the community.

Cheers,

William