Migrating ANTLR v3 grammar to ANTLR v4

Question

We have a grammar written for antlr V3 and I would like to migrate to antlr v4. Is there any migration Guide. and also I would like to know modifications of existing V3 grammar so that we utilize v4 features well.

Answer 1

The biggest hit will be if you used AST Construction and Tree Parsing in v3 or earlier. Huge difference there. You no longer have AST generation (it now generates Parse Trees) or Tree Walkers (you now use Parser Listeners or Parse Tree Visitors).

I haven't seen a migration guide yet, but if you're looking through the v4 docs and currently use ASTs or Tree Walkers, take a look at the v4 sections on Parse Trees, Listeners and Visitors.

Most of the other changes are things to make it easier to write parsers, though some can get you into a little trouble if you're not careful. For instance, you can now write left-recursive rules, but if you depend on a certain precedence (like in an expression grammar), you need to carefully match a few patterns for the ANTLR4 compiler to understand the proper precedence.

I'd strongly suggest getting Ter's book, The Definitive ANTLR4 Reference and just read through it. It gives most of the detail you'll need, though you'll still want to play around a bit.

I've just taken an initial pass at writing a very simple ANTLR4 plugin for Eclipse, and I hope to post it soon. It needs a little more testing, but it's a basic builder so far. Next step is to create an editor...