Older posts made before the Congo rebranding
There is now a syntax converter to convert legacy JavaCC (and some things in JavaCC 21) to the approved CongoCC syntax. You can execute it as: java -jar javacc-full.jar convert filename That will spit it out to stdout. More likely you want something more like: java -jar javacc-full.jar convert filename > outputfilename The converter converts …
The main goal of the JavaCC 21 project, soon to be renamed as CongoCC, is to develop a very capable, practical, usable parser generator tool. However, there is another overarching goal — perhaps not so much a goal, as a philosophy. That can be summed up in a single word: Demystification You see, somehow or …
NFA stands for “Nondeterministic finite automaton”. (Does that make you nervous?) Read More »
(The TLDR: Nested lookahead was always broken in legacy JavaCC. This is finally fully addressed (as of 11/26/2022) in JavaCC 21. However, since this fix has a lot of potential to break existing code, for now, the fix is only in effect if you put LEGACY_GLITCHY_LOOKAHEAD=false at the top of your grammar(s). Meanwhile, you should …
There is a scene that repeats itself in various James Bond films, usually towards the end. The archvillain has captured Bond. However, instead of just killing him, he has to do it in some very creative, slow manner, using some sort of Rube Goldberg contraption. Meanwhile, he tells Bond gleefully what his plans are for …
I shall tell you my plans but then I shall have to kill you, Mr. Bond Van Bruggen Read More »
A very annoying detail in computing (annoying in particular because the whole thing seems so utterly pointless) is this whole issue of line endings in text files. In Microsoft Windows, the operating system that dominates the desktop, a line ending is denoted by "carriage return" followed by "line feed", or CR-LF for short. (Namely the …
♫ I can still hear you saying ♫ ♫ You would never break the chain ♫ ♫ Never break the chain… ♫ Fleetwood Mac What we see frequently with JavaCC is cases where the original authors were actually quite perceptive: they anticipated certain problems and put in some dispositions to deal with them, but unfortunately, …
I recently completed a major refactoring of how the generated Token API works in JavaCC 21. Though this constitutes a quite revolutionary set of changes under the hood it may actually not be all that noticeable to many (or most) users. I think there are basically two groups of users (not mutually exclusive) who would …
(*Note that this article is largely superseded by the one here) JavaCC 21 now has assertions. There are actually two kinds of assertions: The assertion condition is expressed in Java code. The assertion condition is a lookahead expansion. The first kind of condition looks like this: ASSERT {someCondition()} Optionally, the assertion can have a message, …
As the title says: as of this writing, the included grammars for Java and Python both support the latest versions of the language, JDK 17 and Python 3.10 respectively. Contextual Keywords It turns out that, from a language support perspective, the only new stable feature in JDK 17 is the concept of sealed classes. This …
Announcement: JavaCC 21 includes parsers for the latest Java and Python versions! Read More »
Sometimes, when you complete a major code cleanup, features that were previously pie in the sky become low-hanging fruit to pluck. The new feature that I describe here, the ability to activate and deactivate tokens is such a case. It resulted from my rewriting of the lexical code generation that I describe here. In an …
Context-Sensitive Tokenization, Next Installment, Activating and De-activating Tokens Read More »