> For the complete documentation index, see [llms.txt](https://isubasinghe.gitbook.io/isithas-wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://isubasinghe.gitbook.io/isithas-wiki/computer_science/programming_language_theory/semantics/attribute_grammars.md).

# Attribute grammars

## Basic idea

Augment a CFG by attaching *attributes* to grammar symbols and *semantic rules* that compute them. A clean way to fold static analysis (type checking, scope resolution) directly into parsing.

## Key facts

* *Synthesised* attributes flow up from children to parent.
* *Inherited* attributes flow down from parent / siblings.
* S-attributed: only synthesised — evaluable in one bottom-up pass (yacc-friendly).
* L-attributed: synthesised + inherited-from-left-siblings — evaluable in one left-to-right pass (LL-friendly).

1. S-attributed grammars
2. L-attributed grammars