Substring scan assertion with pcre2test fails

[David Wahlstedt]

Hello,

I tried the example of substring scan assertion:

\b(\w++)(*scs:(1).+rh)

from the pcre2pattern man page.

In both pcre2test 10.39 and 10.45 I get:

PCRE2 version 10.45-DEV 2024-06-09 (8-bit)
/\b(\w++)(*scs:(1).+rh)/debug
Failed: error 195 at offset 13: (*alpha_assertion) not recognized
arhg

What am I doing wrong? I haven't turned on dfa_match as far as I know.

Is my version of pcre2 too old? (v10.45 9 june)

BTW, questions about substring scan assertions: is it like groups: option settings that appear inside it last only until its end? Is the scan assertion quantifiable?

BR,

David

[Philip Hazel]

Too old. The substring scan facility was merged into the Git repo on 30th August.

Regards,

Philip

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[David Wahlstedt]

Thanks, now it works!

When I try an empty group list it complains about "reference to non-existent supattern".

So I guess the group list has to be non-empty?

Of course it's weird to use this construction with an empty group list, but from a syntax rule point of view it is good to know.

PCRE2 version 10.45-DEV 2024-06-09 (8-bit)

/a(*scs:())/debug
Failed: error 115 at offset 8: reference to non-existent subpattern
a

The version string above still says 2024-06-09, but it is actually from git today, and it ran the \b(\w++)(*scs:(1).+rh) example successfully.

Regards,

David

[Zoltan Herczeg]

Hi,

yes, the list must not be empty. The error message could be improved.

Regards,
Zoltan

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[Zoltan Herczeg]

Hi,

scan substing is a completely new feature which will be available in
the next release. You can try it if you compile pcre2 from the github
repository. I hope you will like it!

Scan substring is an assertion, it should behave like any other
assertions such as (?=...) . That means it matches to an empty string,
(*ACCEPT) accepts it, etc. Regardless, you can add quantifiers, a {6}
will repeat it 6 times. The ? can also be useful, but * is practically
a ?. Local options are limited to brackets. For example, in the
/()(*scs:(1).(?s).)./ pattern, only the second dot matches to all
characters (including newline).

Regards,
Zoltan