EBNF

A human-friendly form of Regex used for pattern matching.

Element	Syntax
Non-terminal (like variable)	<a>
Assignment	<-
Terminal (literal)	7, a (no angle brackets)
Sequence	<a> <b>
Repetition (0 or more times)	{ <a> }
Optional (0 or 1 time)	[ <a> ]
Choice (alternatives)	<a> | <b>
Grouping	(<a> | <b>) <c>