CongoCC Parser Generator

ancient_history

Anonymous (anonymous@undisclosed.example.com) — 2020-10-30T15:57:10+00:00

JavaCC Project History There are certain questions that I anticipate will be coming up over and over again, so I shall attempt to answer them forthrightly. In the following, I shall outline the history of all of this. People are free to dismiss this as my (Revusky's) opinionated and self-interested version of things. But I would just say this: while not everybody who comes to know me personally ends up liking me, they would (

choice_points

Anonymous (anonymous@undisclosed.example.com) — 2021-02-08T18:09:42+00:00

Choice Points and Lookahead A choice point in a JavaCC grammar is a juncture where the parser must decide between two or more expansions. There are four kinds of choice point: * An optional expansion, i.e. the expansion inside a zero or one construct, which is written

code_injection_in_javacc_21

Anonymous (anonymous@undisclosed.example.com) — 2020-09-29T10:24:05+00:00

Code Injection Note, first of all, that the INJECT statement does not exist in Legacy JavaCC. INJECT allows you to specify extra code that will be placed (or “injected”) in generated java code. It can appear anywhere in your grammar where you could place a BNF production or Token production. It can be written in one of two forms.

contextual_predicates

Anonymous (anonymous@undisclosed.example.com) — 2023-03-03T14:23:26+00:00

Contextual Predicates A contextual predicate allows you to add conditions at choice points based on scanning back in the call/lookahead stack. We are not aware of any other parser generator tool that has this feature. The easiest way to describe this is with some actual examples.

convention_over_configuration

Anonymous (anonymous@undisclosed.example.com) — 2020-10-22T18:19:07+00:00

Convention over Configuration (when possible) It is our considered view that a tool having a plethora of configuration options can make it far less usable. Or, at the very least, if there are a lot of configuration options, the neophyte user should be able to ignore them for the most part. One key aspect of this is having sensible defaults that correspond to the typical usage scenarios. Another aspect is simply having naming conventions so that the tool can infer the names of files and their lo…

deprecated_settings

Anonymous (anonymous@undisclosed.example.com) — 2021-12-21T14:03:24+00:00

Obsolete Settings from Legacy JavaCC (and JJTree) As a result of quite a bit of forward evolution, some of the settings from legacy JavaCC (and JJTree) are obsolete in JavaCC21. We don't anticipate that any of them will be missed. * STATIC: JavaCC21 does not support static parsers. Or, in other words, this is always set to false, (and thus, ignored.)

first_set

Anonymous (anonymous@undisclosed.example.com) — 2020-10-08T12:45:17+00:00

An expansion's first set is simply the set of all tokens that can begin the expansion. The most trivial example imaginable is any expansion that begins with a single token. Thus, the first set of: "foo" "bar" "baz" is simply a set with one element,

include

Anonymous (anonymous@undisclosed.example.com) — 2023-03-03T16:20:32+00:00

The INCLUDE Statement Congo's INCLUDE statement allows you to break up your grammar file into multiple physical files. It would look like this typically: INCLUDE "IncludedGrammar.javacc" This feature is not present in legacy JavaCC. The motivation be

key_differences

Anonymous (anonymous@undisclosed.example.com) — 2023-07-08T07:25:41+00:00

Key Differences between CongoCC and Legacy JavaCC From the end user's point of view, the most important difference is that CongoCC has undergone quite a bit of re-design to make it much more usable “out of the box” than the legacy JavaCC. One of the most basic (and obvious) things that CongoCC provides is the

new_settings_in_javacc_21

Anonymous (anonymous@undisclosed.example.com) — 2022-02-15T05:28:07+00:00

Here is a list of settings that exist in JavaCC 21 but are not (and never were) present in the legacy JavaCC tool: * BASE_NAME This option is used to set the name of the parser, lexer, constants, and NFA data files instead of using the default naming convention that prefixes these files with the name of the grammar file. If this option is set to an empty string (BASE_NAME=

new_syntax_summary

Anonymous (anonymous@undisclosed.example.com) — 2023-04-10T10:04:31+00:00

Overview of the Newer Streamlined Syntax The following is a summary of CongoCC's streamlined syntax from the perspective of somebody migrating from legacy JavaCC. Note that, unlike CongoCC's predecessor, JavaCC 21, CongoCC does not support the legacy syntax. Any existing grammar file must be converter. There is a utility available that automatically converts the legacy syntax to the streamlined syntax. You can pick up the

nothingburger

Anonymous (anonymous@undisclosed.example.com) — 2020-10-02T01:54:09+00:00

Nothingburgerism Where's the Beef? (Classic Wendy's Commercial) As I describe here, at some point in mid-2008, I set myself the task of figuring out what the JavaCC “community” had achieved, what work they had done on the code in the five years since it had been open-sourced on java.net.

scan_statement

Anonymous (anonymous@undisclosed.example.com) — 2021-08-07T08:21:32+00:00

The new SCAN Statement JavaCC 21 introduces a new SCAN statement that is designed to supersede the legacy LOOKAHEAD. It is a key part of the newer streamlined syntax. Like LOOKAHEAD, SCAN exists to specify conditions at choice points that override the default resolution mechanism of scanning ahead exactly one token. The new

settings

Anonymous (anonymous@undisclosed.example.com) — 2023-04-17T18:53:04+00:00

Here, by category, is a list of all the settings in CongoCC that can be set at the top of a grammar file. Options relating to File/Class/Package Naming By default, the tool has some naming conventions that, actually, you might as well use. For example, if your grammar lies in a file named

start_hacking

Anonymous (anonymous@undisclosed.example.com) — 2023-05-06T17:25:10+00:00

Start Hacking! CongoCC is based on the idea that things should just work. If all you want to do is use the tool, all you need to do is download the file: There are no dependencies (aside from a JDK) and it should be runnable via: java -jar congocc.jar

start

Anonymous (anonymous@undisclosed.example.com) — 2023-02-19T00:56:49+00:00

What is CongoCC? CongoCC is a more advanced version of the legacy JavaCC tool. The current version is the result of a huge amount of restructuring and refactoring with the following main goals: * To make the tool much more useful and usable, out of the box

technical_support

Anonymous (anonymous@undisclosed.example.com) — 2023-05-06T17:23:13+00:00

Technical Support Our policy is that we only provide technical support for the latest version of the tool. That is the version that you can download at . Alternatively, your own build is fine as long as it is built from the latest version of the code

tree_building

Anonymous (anonymous@undisclosed.example.com) — 2020-04-25T18:15:58+00:00

Tree Building Enhancements in JavaCC 21 In JavaCC 21, there is no separate program analogous to legacy JavaCC's JJTree preprocessor. Building an AST is assumed to be the way that most people will want to use the tool, so parsers generated by JavaCC 21 build a tree *by default*. If you really don't want to build a tree (or you want to build a tree but in your own java code actions) there is a

up_to_here

Anonymous (anonymous@undisclosed.example.com) — 2023-03-03T14:26:56+00:00

The "Up-to-here" Marker The up-to-here marker =>|| and the up-to-here-plus marker =>|+n (where n is an integer) were introduced to be able to express lookahead in a more succinct and less err-prone manner than using the LOOKAHEAD from legacy JavaCC or even the terser