PEG
Parsing Expression Grammar (PEG) is a formal grammar notation used to describe syntax for parsing, particularly in programming languages and data formats. It defines a set of rules that specify how to match input strings, using ordered choice and greedy matching to avoid ambiguities common in context-free grammars. PEGs are often implemented in parser generators or libraries to create efficient, deterministic parsers.
Developers should learn PEG when building parsers for domain-specific languages, configuration files, or data serialization formats, as it provides a clear, unambiguous syntax specification that leads to predictable parsing behavior. It is especially useful in tools like text editors, compilers, or data processing pipelines where reliable syntax analysis is critical, and its deterministic nature simplifies error handling and debugging compared to traditional parsing methods.