What this article’s title alludes to is the fact that, once you have a complex language (or system) there are usually multiple equally valid ways to say something. Let’s consider the following typical case, a comma-separated list of some sort, something like: [1, 2, x, y, “Hello, World”] To describe the grammar for this in …
You say “Tomayto”, I say “Tomahto”. Exploring Syntax options in CongoCC. Read More »
It has long been a nagging thing in my head that there is a basic flaw with token lexical actions in CongoCC. Well, first things first. What is a token lexical action, you might be wondering. What I’m talking about is something like: TOKEN : <FOO: "foo"> {some java code here, this is the token …
Tokenization Enhancements with some Tips and Tricks Read More »
Folks, the good news is that I just fixed this longstanding glitch in CongoCC. The bad news is that the fix is not 100% backward compatible. Well, granted, the above does kind of beg the question of WTF the code prologue glitch is. Though probably the question that will occur to most people is more …
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 …