undefined<R> function Null safety

SettableParser<R> undefined<R>(
  1. [String message = 'undefined parser']
)

Returns a parser that is not defined, but that can be set at a later point in time.

For example, the following code sets up a parser that points to itself and that accepts a sequence of a's ended with the letter b.

final p = undefined();
p.set(char('a').seq(p).or(char('b')));

Implementation

SettableParser<R> undefined<R>([String message = 'undefined parser']) =>
    failure<R>(message).settable();