peg — odinpkg

# Odin PEG Engine

A fast, dynamically compiled Parsing Expression Grammar (PEG) engine written in Odin.
It strictly handles **Syntax**—acting as a scannerless,
unambiguous parser that reads text and generates a structured,
labeled Abstract Syntax Tree (AST) using a virtual memory arena.

## Project Structure
```text
peg_engine/
 ├── core.odin         # Core VM, Context, and recursive evaluation loop
 ├── utils.odin        # Helper functions and memory utilities
 ├── grammar/
 │    └── builder.odin # Meta-compiler (turns grammar strings into runnable engines)
 └── tests/
      └── main.odin    # Implementation tests

Grammar Syntax

Operator	Type	Description
`"abc"` / `abc`	String	Matches exact text.
`'a'-'z'`	Range	Matches a character within the range.
`.`	Any	Matches exactly one character.
`A B`	Sequence	Matches `A` followed immediately by `B`.
`A\|B`	Choice	Ordered choice. Tries `A`, if it fails, tries `B`.
`A*`	Zero-or-More	Matches `A` zero or more times.
`A+`	One-or-More	Matches `A` one or more times.
`A?`	Optional	Matches `A` zero or one time.
`&A`	Lookahead	Succeeds if `A` matches. Does not consume text.
`!A`	Not-Predicate	Succeeds if `A` does not match. Does not consume text.
`(A B)`	Grouping	Groups expressions together.

AST Generation & Rules

Syntax	Description
`Rule = A`	(Not implemented) Defines a reusable grammar rule.
`RuleName`	(Not implemented) References a previously defined rule.
`<Name>A`	Capture: Wraps the matched text in an AST node named `Name`.
`lbl:A`	Label: Tags the captured node with the label `lbl`.

Example Usage

1. The Grammar

//TODO

2. The Output AST

If the engine parses x = 500, it generates this labeled tree structure in memory:

[AssignExpr]
 ├── target: [Variable] "x"
 └── value:  [Integer] "500"