Lexer Generator Skill

Overview

Expert skill for generating and hand-writing lexers using various approaches including DFA-based lexers, table-driven lexers, and hand-written recursive lexers.

Capabilities

• Generate lexer from regular expression specifications
• Implement maximal munch tokenization
• Handle Unicode character classes and normalization
• Implement efficient keyword recognition (tries, perfect hashing)
• Support incremental/resumable lexing for IDE integration
• Generate lexer tables and state machines
• Handle lexer modes and contexts (e.g., string interpolation)
• Implement error recovery with skip-to-next strategies

Target Processes

• lexer-implementation.js
• language-grammar-design.js
• lsp-server-implementation.js
• repl-development.js

Dependencies

• Flex-like generators
• RE2/Hyperscan libraries

Usage Guidelines

1. Token Definition: Start by defining the complete set of tokens with their regex patterns
2. Maximal Munch: Always implement maximal munch to handle ambiguous token boundaries
3. Unicode Support: Consider Unicode normalization forms and character classes from the start
4. Error Recovery: Implement skip-to-next-valid strategies for robust error handling
5. Performance: Use table-driven approaches for large token sets, hand-written for simple lexers

Output Schema

{
  "type": "object",
  "properties": {
    "tokens": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "name": { "type": "string" },
          "pattern": { "type": "string" },
          "priority": { "type": "integer" }
        }
      }
    },
    "lexerType": {
      "type": "string",
      "enum": ["dfa", "table-driven", "hand-written"]
    },
    "generatedFiles": {
      "type": "array",
      "items": { "type": "string" }
    }
  }
}