Grammar Syntax

This document outlines how to write .gram files. It useful to refer to parsergen/metagrammar.gram for the exact specification, or look at the readme file for an example. Rules must follow the form of identifier : <terminals / non terminals> <optional action>; The current implementation is almost as complete as seen here.

Expression	Description
A B	Sequence A followed by token B
A*	token A is repeated zero or more times
A+	token A is repeated one or more times
A?	token A is optional
A | B	there is either token A or B
(A B)	there is a group A B, these tokens are grouped into a list
v=A	the token A is assigned to variable v
x	Points to statement x
expr : v=A { v };	see previous, the return expression is v

Note: actions must contain a valid python expression which can go after a return statement.

Multiple Rules

expr
    : A B;
    : B A;

The expr rule can be either A B or the alternative rule B A.