On Wed, 11 Jul 2018, ND via Pcre-dev wrote:
> I seen this docs before.
> But in example verb not appears inside assertion. It appears after it.
The (*MARK) is inside the assertion. That is what matters. I have
updated the documentation to say this:
The search for a (*MARK) name uses the normal backtracking mechanism,
which means that it does not see (*MARK) settings that are inside
atomic groups or assertions, because they are never re-entered by
backtracking. Compare the following pcre2test examples:
re> /a(?>(*MARK:X))(*SKIP:X)(*F)|(.)/
data: abc
0: a
1: a
data:
re> /a(?:(*MARK:X))(*SKIP:X)(*F)|(.)/
data: abc
0: b
1: b
In the first example, the (*MARK) setting is in an atomic group, so it
is not seen when (*SKIP:X) triggers, causing the (*SKIP) to be
ignored. This allows the second branch of the pattern to be tried at
the first character position. In the second example, the (*MARK)
setting is not in an atomic group. This allows (*SKIP:X) to
immediately cause a new matching attempt to start at the second
character. This time, the (*MARK) is never seen because "a" does not
match "b", so the matcher immediately jumps to the second branch of
the pattern.
This is exactly the same behaviour as Perl.
Philip
--
Philip Hazel
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