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 …
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 »
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 in: ASSERT {x!=y} : “At this point, x and y …
It had been in the back of my mind nagging me for some time, thinking that we would eventually need some sort of preprocessor functionality moving forward, to support output for different programming languages (besides Java) and actually, even different Java targets. I had also been looking more closely at C# recently and finally, I …
Before getting into what the minor enhancements to tree building are, I guess I should write a quick synopsis of the current state of affairs. When you have TREE_BUILDING_ENABLED set to true (this is the default in JavaCC21) the tree building machinery will build a Node if the production results in the creation of more …
Tastes just like home-made! (Some more tree building enhancements) Read More »
When I say "fully supported", I mean all the new features that are categorized as "stable". In fact, the only new language feature that has been promoted to stable in JDK 14 is the new syntax for the Switch statement. This also allows a Switch statement to be used as an expression. In fact, the …
(N.B. Note added 13 June 2021: This article is useful in terms of understanding how to add token hooks to code. However, in terms of solving the specific problem outlined, the article is obsolete. See here for the updated solution.) Since I picked up my work on the JavaCC codebase at the end of 2019, …
“You can’t get there from here!” — The Problem of Context-Sensitive Tokenization Read More »
The FAIL construct is really pretty dead simple. Here is an example: A. ( “foo” | “bar” | FAIL “Was expecting \”foo\” or \”bar\” here!” ) At first I thought the above was just syntactic sugar, since you can, of course, already write: B. ( “foo” | “bar” | {throw new ParseException(“Was expecting \”foo\”or “\bar\” …
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 …