regex-syntax

regex-syntax is the Crystal port of Rust's regex-syntax crate used by Logos. It parses regex patterns into a typed HIR (high-level intermediate representation) that is consumed by regex-automata.

Installation

Add to shard.yml:

dependencies:
  regex-syntax:
    github: dsisnero/logos
    path: lib/regex-syntax

Then run:

shards install

Usage

require "regex-syntax"

hir = Regex::Syntax.parse("[a-z]+")
puts hir.class                       # Regex::Syntax::Hir::Hir
puts hir.complexity                  # priority heuristic
puts hir.has_greedy_all?             # greedy-dot detection
puts hir.can_match_empty?            # empty-match analysis

Supported constructs (Logos-focused)

• Literals and concatenation
• Alternation (|)
• Character classes ([], \d, \w, \s, unicode properties)
• Repetition (*, +, ?, {m,n})
• Captures and non-capturing groups
• Start/end and word-boundary assertions (^, $, \A, \z, \Z, \b, \B)
• Inline flags used by Logos (i, u)

Development

From this directory:

crystal tool format src spec
crystal spec

For full-repo checks, run from repository root:

ameba src spec
crystal spec

Upstream reference

• Rust source of truth: vendor/regex-syntax/
• Crystal integration points:
  • lib/regex-automata/
  • src/logos/macros.cr

License

MIT