What is an example of use case for epsilon in dart petitparser?

Question

I don't understand the comment:

/// Returns a parser that consumes nothing and succeeds.
///
/// For example, `char('a').or(epsilon())` is equivalent to
/// `char('a').optional()`.
@useResult
Parser<void> epsilon() => epsilonWith<void>(null);

Could someone give a specific example?

The best answer I've found to deep petitparser questions is to study the tests, or study the examples repo. — Randal Schwartz, Jul 18 '23 at 16:32

score 2 · Accepted Answer · answered Jul 18 '23 at 17:06

It appears to do exactly what it says. Instead of writing "foo = optional bar" you can define a step with "foo = bar or epsilon".

In the "indent" parser in the repo, I see it is used to attach .where and .map options with side-effects. You can check that out for details.

What is an example of use case for epsilon in dart petitparser?

1 Answers1