pgpg

PGPG is the Pretty Good Parser Generator. As of Feburary 2023 it is very much a sketch and a work in progress.

Goals

Implement a few basic algorithms.
Reuse code whenever possible
- Across multiple algorithms like LALR/LR
Make good use of classes -- e.g. lexer.match() rather than global match() which are commonly used in intro-to-parsing textbooks.
Be lucid above all else. Lexing/parsing is ubiquitous in the modern world, and forms a large part of our world. Yet sadly such tools are too often arcane and confusing. PGPG is transparent, inclusive, and explains itself openly.
Offer choices.
- Sometimes a parser-generator is overkill -- for simpler grammars, a hand-written lexer and a hand-written recursive-descent parser are quite satisfactory. PGPG offers reusable, easy-to-understand examples here.
- Sometimes a hand-written lexer/parser is underkill -- yet parser-generators can be complex and intimidating. Here, too, PGPG offers reusable, easy-to-understand examples.
- PGPG offers classes that reduce code-duplication for various lex/parse implementations: you can reuse what you want, and hand-write what you want.
- PGPG offers grammar-to-parser all in one process invocation, or parser-generate to language-independent storage (probably JSON), or traditional parser-generate directly to implementation-language code.

Implementation initially in Go
- Maybe Python and/or Rust later
- Aim for non-clever abstraction and concept reuse
- Try to use language-independent data structures when possible
Generator target initially Go
- Maybe Python and/or Rust later
- Try to use language-independent data structures when possible

Self-education and experimentation
Promotion of parser-generation knowledge
I would like to ultimately use this in Miller
I'd love to get some code of ad-hoc code-sed/code-grep/etc functionality going for, say, Go, Python, JS, etc. wherein program text would be treated as a stream where the "sedding" and "grepping" would be done at the abstract-syntax-tree level. Do note however that Python and JavaScript offer library access to their own parsers, with tree-walk-visitor callbacks which are simply splendid.