This is a simple demonstration of the negative look-behind operator.
The grammar defines two types of text (ASCII printing characters,)
Comment text begins with //, other text does not.
Both of these input lines will parse successfully.
Look at the trace to see that in the one case other-text is matched,
while in the other case comment-text is matched.
In a more realistic application the AST would be used to translate
or otherwise distiguish between the two types of text.
(function negative() {
let input = '// this is a comment';
const grammar = new (require('./negative-grammar'))();
const setup = require('./setup');
setup(input, grammar, 'negative-comment');
input = 'this is not a comment';
setup(input, grammar, 'negative-no-comment');
})();