CongoCC Cheat Sheat available?

Jens

Happy New Year to all participants!
I have played a little bit with CongoCC in the last few days and was a little bit frustrated about the scattered documentation. I have seen there is a sceleton document for CongoCC available but I miss a brief description of all available configurations and features.

revusky

Jens

Well, I wrote the last response based on the assumption that, whatever docs (meagre that they are) you had found them. But... maybe not...

Have you looked at this one?

Actually, I just looked through it and at least one thing there is wrong. (Probably more than one thing...) So, for example, MINIMAL_TOKEN is set to true by default now. Well, I need to look over some of these pages and fix things that are now wrong! But anyway, again, if there is anything that is unclear, by all means just ask about it.

revusky

Hi Jens, Happy New Year. Nice to see you here.

Well, let's see... to answer your question, probably there is not any documentation that you have not already found! And, of course, what there is is quite scattered. And something really needs to be done about this.

You know, one real issue is that far too much of the stuff that I have written is based on the assumption that the reader is already familiar with legacy JavaCC. So, I devote a lot of energy into explaining to the reader why JavaCC21 (now renamed to CongoCC, as you doubtless know) is so much better than the legacy JavaCC -- which, false modesty aside, it is... but somehow it doesn't seem to matter so much.

So, I mean, yeah, really, there is a need for a fresh start, I think -- some documentation that assumes no prior knowledge of JavaCC and just starts from the beginning, probably not even assuming prior knowledge of parser generators generally.

So, certainly a sort of cheat sheet is a good idea. Also, maybe just a sort of quickstart document. Meanwhile, the best advice I could give is probably just to study the existing grammars. The JSON grammar is quite simple really. Also, there is an arithmetic example, that I have long meant to write a tutorial around.

By the way, have you looked at the newest FreeMarker 3 grammar? I think that provides some good examples of how to solve certain parsing problems with CongoCC. Though, admittedly, it's not exactly a beginner example, like the arithmetic example or the JSON grammar. But that grammar (along with the Python/Java/C#/Lua grammars of course) provides some decent examples of how to do various things.

But, look, generally speaking, anything you come across that you are confused about, do feel free to write any questions about it here. That could end up being helpful in terms of working up a cheat sheet maybe.

By the way, have you looked at the newest FreeMarker features? If you have any feedback on that, by all means. Maybe best to write it as a response to the "Resuscitating FreeMarker" post on this forum.

Jens

Hi Jonathan, thanks for the quick reply. I think I have found all helpful pages for JavaCC and CongoCC. Currently the biggest problem is to sort all sources in chronological order, because you develop to much to fast 😄
I have one question at the moment. It is possible to ignore INJECT statements from included grammar files?

revusky

Jens Hi Jonathan, thanks for the quick reply. I think I have found all helpful pages for JavaCC and CongoCC. Currently the biggest problem is to sort all sources in chronological order, because you develop to much to fast 😄

Are you, by any chance, going over the latest FreeMarker code?

If so, that is actually a pretty good thing to do, since the FreeMarker grammar there may well be the best example available of CongoCC usage for a fairly complex language. I think that if you went over that grammar and came to understand it, you'd be in a pretty good position in terms of understanding CongoCC overall. Well, that's true of the Java grammar or the C# or Python grammars too, but the FreeMarker grammar was basically written over the summer so it tends to really utilize the latest CongoCC feature set.

I have one question at the moment. It is possible to ignore INJECT statements from included grammar files?

Well, at the moment, there is no disposition for that. I guess what one could do in some cases is use the preprocessor.

You could have, in the included grammar something like:

#if !exclude_certain_injections // exclude_certain_injections is false by default

INJECT ....

INJECT ....

#endif

And then in the including grammar, you could have:

#define exclude_certain_injections
INCLUDE "included_grammar.ccc"

And the INJECT statements in the included grammar would be ignored.

Of course, maybe that doesn't address the problem so well, since the idea is that we have certain standard grammars right in the jarfile that can be INCLUDEd, so you can write:

 INCLUDE JAVA

And it just fishes the Java.ccc grammar out of the congocc.jar and includes it at that point. And in that case you don't have any chance to add any preprocessor snippet to the included grammar.

That said, I'm not sure how often there is such a strong need to turn off an INJECT. I mean, okay, if you're not going to use any of the injected code yourself, it's injected anyway, which is a bit inefficient space-wise. But it is probably not of very much practical importance nowadays.

There are a whole bunch of injected methods in the FreeMarker grammar, typically used when the rendering machinery walks the tree, and if you were going to INCLUDE the FreeMarker grammar for some other purposes, then a lot of those injected methods (and injected fields they use) are maybe unneeded. But really, that they're there occupying extra space does not seem like a big problem typically. Nowadays anyway.

And, of course, you can add your own injections in the including grammar...

Or maybe you have some other reason to want to suppress code injections. I don't know your use case.

So I guess the short answer is that there is no general ay to disable injections in the included grammar from the including grammar. But if you have an included grammar and you anticipate the need to turn off the injections, you can add a bit of preprocessor code as above.

I hope that answers your question.

Jens

Hi Jonathan, sorry for the late reply but i was busy in the last days (but i wrote a small blog entry about DSL generation with CongoCC). I will start my new job in a few weeks and have the plan to dive deeper into the CongoCC/FreeMarker code.