[[[link spirit.qi.reference.operator.not_predicate `!a`]]
[`Unused`] [Not predicate. If the predicate `a` matches,
fail. Otherwise, return a zero length match.]]
[[[link spirit.qi.reference.operator.not_predicate `!a`]]
[`Unused`] [Not predicate. If the predicate `a` matches,
fail. Otherwise, return a zero length match.]]