Antlr 3 to Antlr 4 Migration Guide

[UnquietCode]

Upgrading from 2 to 3 had a nice migration guide (thanks for that). It would be helpful if there were one included for the upgrade from 3 to 4, either as a wiki page or referenced in the readme.

[parrt]

Hi. I think we should create one. ok, got something started here:

https://theantlrguy.atlassian.net/wiki/pages/viewpage.action?pageId=1900596

[SomMeri]

Thank you for the page, it already helped. I have one more question:

If hypothetical grammar does not uses ast ^(), but uses a lot of syntactic/semantic predicates, will it work the same way as before? What I mean is, predicates located in the beginning of the rule/alternative used to be hoisted, are they still going to be hoisted? And those in the middle of alternatives were never hoisted, is it still the case?

[sharwell]

There is no more "hoisting" in the fashion that ANTLR 3 had it. Predicates located at the left edge of a decision (i.e. the left edge of a rule or block with more than one alternative) are evaluated as part of making that decision. Other predicates are ignored.
[parrt edit: others are ignored as part of decision. They are still evaluated during the parse.]

[SomMeri]

@sharwell Thank you.

[miho]

Thanks for starting the migration guide. Just tried to construct my own grammar. It was damn easy. ANTLR 4 scares me. It just works :)

You mention that ASTs are no longer possible. What should I do if i'd like to write a compiler. Are parse trees equivalent to ASTs? Some additional hints on this topic would be great.

[parrt]

For writing a compiler, either generate LLVM-type static-single-assignment form stuff or construct an AST from the parse tree or using actions in grammar, turning off auto-parse-tree construction.

[UnquietCode]

Thanks this is nice.

[parrt]

Updated the wiki page a bit more with links etc...

[vegtelenseg]

I am planning on upgrading to V4 from V3, I tried following the link Terence shared, but seemingly it does not exist anymore. Is there any source that I could follow to complete this upgrade?

Thanks in advance.

[parrt]

all doc has moved to repo https://github.com/antlr/antlr4/tree/master/doc not sure how much info on upgrading is there.

Try the faq https://github.com/antlr/antlr4/blob/master/doc/faq/general.md

[vegtelenseg]

I read through it and unfortunately did not find what's pertinent to what I am trying to do. I have asked a question here though, that is specific to what I am struggling to solve. http://stackoverflow.com/questions/36858750/converting-from-antlr3-to-antlr4

[ericvergnaud]

The best place for discussion is the google group.

Le 26 avr. 2016 à 19:12, Siyanda notifications@github.com a écrit :

I read through it and unfortunately did not find what's pertinent to what I am trying to do. I have asked a question here though, that is specific to what I am struggling to solve. http://stackoverflow.com/questions/36858750/converting-from-antlr3-to-antlr4 http://stackoverflow.com/questions/36858750/converting-from-antlr3-to-antlr4
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[filipegmiranda]

Hi @ericvergnaud - can you share the google group in here?

[ericvergnaud]

https://groups.google.com/forum/#!forum/antlr-discussion <https://groups.google.com/forum/#!forum/antlr-discussion>

…

Le 25 sept. 2017 à 20:56, Filipe Miranda ***@***.***> a écrit : Hi @ericvergnaud <https://github.com/ericvergnaud> - can you share the google group in here? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#464 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ADLYJOUO_bQq5b3e4UMOqLlV94cUbWc2ks5sl6LygaJpZM4Bh3UK>.

[ArsenShnurkov]

The link from the comment #464 (comment) is no longer valid. Where one can find the migration guide now ?

[parrt]

It doesn't look like anything exists beyond that faq entry