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Re^2: YAML::XS perl/regexp (?u:(?u:
by shmem (Chancellor) on Dec 06, 2017 at 22:07 UTC
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YAML should store the pattern (( re::regexp_pattern($re) )[0] ) and the modifiers ( ( re::regexp_pattern($re) )[1] ) separately.
...and YAML::XS should make use of XS(XS_re_regexp_pattern) in universal.c to achieve that. Inevitably, this raises backcompat issues.
perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'
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and YAML::XS should make use of XS(XS_re_regexp_pattern) in universal.c
And how does one do that? XS(XS_re_regexp_pattern) creates the Perl sub re::regexp_pattern, so that's a very weird way of saying that YAML::XS should call Perl sub re::regexp_pattern.
Inevitably, this raises backcompat issues.
This can be addressed by storing them as a different type than perl/regexp (perl/regexp_plus_mods?).
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i think shmem was talking about regexp_pattern only available since perl 5.10, while YAML and YAML::XS aim to spport 5.8. I wonder how your suggeestion addresses that. Can you elaborate or did you mean something else?
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Re^2: YAML::XS perl/regexp (?u:(?u:
by tinita (Parson) on Dec 08, 2017 at 16:54 UTC
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It would be possible to store a regex as a sequence and use the same tag for it:
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re1: !!perl/regexp (?^usi:pattern)
re2: !!perl/regexp [ pattern, isu ]
For perl 5.8 the old behaviour could be used. This could be done for YAML and YAML::XS. Possibly also for YAML::Syck, which has the same problem, but I would have to ask Todd, the maintainer. | [reply]
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You can add understanding of !!perl/regexp [ pattern, isu ] at any time, but backwards compatibility requires making the generation of that an option. Eventually, once support has been established, it could default to the new method.
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Another possibility would be to continue just using a string. Check with regexp_pattern(), if there are any flags (ignoring u), just store the stringified regex, otherwise store the pattern itself.
This would still lead to unnecessary (?:...) but it wouldn't grow in roundtrips.
Have been looking into universal.c how regexp_pattern() is implemented. At the moment it's too much magic for me to understand.
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