If you liked LOOKAHEAD, then you’ll love LOOKBEHIND! Actually, I have not added LOOKBEHIND as a new keyword in JavaCC. It is just an informal way of referring to a new feature that I recently added. I implemented this because I realized that there was a very common thing people want to do in a JavaCC grammar …
A few months ago, I started re-examining some of the legacy JavaCC syntax. I realized the pure absurdity of having to write: LOOKAHEAD(Foo() Bar() Baz()) Foo() Bar() Baz() In short order, I allowed people to write the above as: LOOKAHEAD Foo() Bar() Baz() But this started me thinking…. I reasoned that there were doubtless plenty …
In my last post I reported that I had finally fixed the way syntactic lookahead works in JavaCC. This leads to the natural question: what about semantic lookahead? Well, what is historically called semantic lookahead in JavaCC is actually misnamed. It’s really just a bit of java code that is used to determine whether to enter an expansion or not. Something like: …
Fixed a Longstanding Bug Known Issue in JavaCC: Nested syntactic lookahead now works! There is a quite serious bug (let’s just call it by what it is, shall we?) of very long standing in JavaCC. Basically, syntactic lookaheads do not nest. This bug is documented in Theodore Norvell’s JavaCC FAQ, which by the way, is the best …
Bugfix! Nested syntactic lookahead now works correctly! Read More »
The overarching design goal of the JavaCC 21 project (dating back from when it was still called FreeCC) is to transform the legacy JavaCC tool into something more useful and useable. Having a clean syntax does not, in itself, further the first goal, but it is surely a key part of the latter. While it is possible for …
Reducing Visual Clutter: Introducing a New Streamlined Syntax for JavaCC 21 Read More »
Some years back, I was traveling with a couple of Spanish friends, and this was late 2012. We were in Kunming, China and came across a poster that advertised some live music. I was fumbling around for a pen and a bit of paper to jot down the information. I thought to ask my traveling …
It’s Official! The Gigabyte is the new Megabyte! Hurrah! Read More »
A bit over a month ago, I wrote about my intention of tearing out support for “JAVACODE” productions. A JAVACODE production is really just a Java method that is like a pretend grammatical production. I could find very few JavaCC grammars in the wild that used this. I asked whether anybody would miss them and …
One of the very basic goals of this iteration of work on the JavaCC codebase, JavaCC 21, is to turn this into a capable tool for generating fault-tolerant parsers. Traditionally, not just JavaCC, but tools in this space generally, consider that it is their job to parse, i.e. to break down input into its various pieces …
A couple of weeks ago, I implemented a solution to a longstanding Dmitry Dmitriyevich problem with LOOKAHEAD specifications in JavaCC. Dmitry Dmitriyevich (alternatively Ivan Ivanovich or Vladimir Vladimirovich) is my own personal terminology for situations where you are required to write highly repetitive code. (Patriotic Irishmen are welcome to call this the Patrick Fitzpatrick or Gerald …
As a result of some private correspondence with one of the PMD developers (PMD makes extensive use of JavaCC) I started thinking about some issues that I had in the back of my mind to look into at a later point. Having recently ripped out the code in JavaCC 21 that supported putting LOOKAHEAD specifications …
Revisiting LOOKAHEAD in JavaCC, Attacking the Dmitry Dmitriyevich Problem Read More »