Assertions, implemented in late 2021, are certainly an important feature in CongoCC — actually pretty much essential when writing grammars for very gnarly languages. However, as currently implemented, they are admittedly a somewhat strange hybrid construct. The main reason for this is that ASSERT has completely different semantics depending on whether you hit the assertion …
Revisiting Assertions, introducing the ENSURE keyword Read More »
I was trying to think back to when most students are introduced to basic algebra. A typical sort of exercise is simplifying unnecessarily complex expressions, so he can rewrite: (x + 1)y -y as: xy Well, regardless of the exact age when people first see such things, this is part of a typical middle school …
As the title says: as of this writing, the included grammars for Java and Python both support the latest versions of the respective languages, i.e. JDK 22 and Python 3.12. New Java Language Features Java language features that were not supported until quite recently were: Record patterns introduced as a stable feature in JDK 21. …
Announcement: CongoCC includes parsers for the latest Java and Python versions! Read More »
First of all, here is an instant gratification download link: freemarker3.jar. I guess that can be considered a preview version of a long-awaited FreeMarker 3.x release. For most typical usage, it is (at least for the moment) a drop-in replacement of older versions of FreeMarker. Actually, this is the same FreeMarker version that is contained …
Let’s consider the multiline comment in Java (and C/C++/C#, among others) which, you surely know, looks like this: /* * Comment text. */ This is an interesting construct. Paradoxically, it is extremely simple — I mean to describe in natural, human language (English or whatever) — but shockingly difficult to express in CongoCC. Or, that …
The poster child for this feature would be something like the C-style multiline comment, i.e. /** * comment */ It is actually surprisingly difficult to specify this in legacy JavaCC (or JavaCC21/Congo up until very recently). One way is to break it into multiple regexp patterns using the MORE feature. Or, alternatively, there is actually …
The following essay outlines the main evolution in the API generated by CongoCC from its origins in the Dark Ages up until now. The Journey of a Thousand Leagues Begins with a Single Step Let’s say you go on an excursion to a national park and there is a well known hiking trail that goes …
Some days ago, I added a new setting. If, at the top of your grammar, you write: TERMINATING_STRING=”some string”; this means that the input you’re parsing is guaranteed to end with that string. If the file ends with that string already, then it does nothing. Otherwise, it tacks that string to the end. In actual …
The TERMINATING_STRING setting, a new (and quite minor!) feature Read More »
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 »