Skip to content

Features

Designing a language is hard. You have to parse source text, produce a semantic model, resolve references, manage multi-file workspaces, and provide a good editing experience. Pegium handles that framework work so you can focus on the semantics of your language.

This chapter covers the main areas Pegium addresses:

  • grammar and parsing
  • semantic models
  • cross-references and linking
  • workspace management
  • editing support

Grammar and parsing

You write grammars directly in C++ through PegiumParser subclasses. Parser expressions cover terminals, named rules, repetitions, lookahead, skippers, and infix parsing. The runtime includes expectation tracking and recovery-aware behavior, so parsing is more than a one-shot syntax check.

Semantic models

Pegium does not stop at syntax trees. AST nodes are ordinary C++20 types, so the semantic model of your language stays directly visible in your codebase. The CST remains available for source-aware tasks such as formatting, comment handling, and precise editor selections. Semantic logic, tooling, and source mapping live in one runtime model.

Cross-references and linking

Real languages need names to resolve to declarations. Pegium models references explicitly through the reference pipeline: name computation, scope computation, scope providers, linking, and workspace indexing. Once wired, the same information drives linking, completion, rename, and navigation.

Workspace management

Most languages quickly become multi-file. Pegium includes shared workspace services that track documents, indexing, and rebuilds across a project. References and diagnostics work across files instead of one isolated parse result.

Editing support

Language servers sit on top of the same document and semantic model. The default service set already covers a broad range of LSP features: completion, hover, definition, references, rename, document symbols, and code actions.

Formatter, validation, completion, hover, and other features remain explicit services. Keep the defaults where they fit and replace only the parts specific to your language.