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Re: RFC: seeking syntax for allowing script run pattern matching

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July 6, 2016 23:21
Re: RFC: seeking syntax for allowing script run pattern matching
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>                                                we have exactly that
>concept with the flags and /(?f:...)/ construct.

It doesn't make sense as a flag in this way.  The existing flags affect
the interpretation of individual regexp elements, so turning them on and
off locally has obvious semantics.  But the script-run feature affects
the meaning of a whole group.  /(?a:\w)(?a:\w)/ means the same thing
as /(?a:\w\w)/, but /(?S:\w)(?S:\w)/ wouldn't mean the same thing as
/(?S:\w\w)/.  It does need affordance to apply it to an arbitrary group,
but flag syntax is the wrong way to get that.  I therefore favour the
/(*sr:...)/ type of syntax.

>That also implies it can be locally disabled:
>  /(?S:\w+ (?-S:\w) \w+)/

Still doesn't make sense as a flag, but there's room for another grouping
operator that makes its content invisible to the immediately-surrounding
script-run constraint.  /(*sr:\w+ (*srhide:\w) \w+)/.

>I think the first (where +S is introduced when it is already active)
>should be a noop - the same script should still be required.
>I think the second (where +S is introduced in a -S scope, itself within
>a +S scope) should permit a new script.

These are the obvious semantics for nesting (*sr:...) and (*srhide:...).

>I wonder whether the next request will be a variant that overrides /./
>to be equivalent to /(?S:\W|\w)/.

What's that supposed to achieve?  Any single character automatically
satisfies the script-run constraint.

>Should the proposal also affect uses of \w inside character classes?

Yes.  The script-run constraint should apply to the sequence of characters
actually matched (except for characters hidden in a nested (*srhide:...)),
regardless of the constructs used to match them.


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