[ruby-core:40826] Re: [ruby-trunk - Feature #5588] add negation flag (v) to Regexp

It is not to hard to negate a regexp, though. Simply wrap it as negative lo=
ok-ahead.

Konstantin

On Nov 7, 2011, at 23:04 , Suraj Kurapati wrote:

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> Issue #5588 has been updated by Suraj Kurapati.
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> Note that I am not asking for the ability to take an arbitrary regexp and=
 construct its negated form (that is a hard problem).  Instead, I am asking=
 for a flag that simply inverts how a regexp is treated by the =3D~ and !~ =
operators (this is not a hard problem).  The negation flag should not chang=
e the Regexp#source of a regexp.
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> Thanks for your consideration.
> ----------------------------------------
> Feature #5588: add negation flag (v) to Regexp
> http://redmine.ruby-lang.org/issues/5588
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> Author: Suraj Kurapati
> Status: Open
> Priority: Normal
> Assignee:=20
> Category:=20
> Target version:=20
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> Please add a negation flag (v) to regexps which inverts them:
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>  "ruby" =3D~ /perl/v       #=3D> true   (turn on negation)
>  "ruby" !~ /perl/v       #=3D> false  (turn on negation)
>  "ruby" =3D~ /(?v:perl)/   #=3D> true   (turn on negation)
>  "ruby" !~ /(?v:perl)/   #=3D> false  (turn on negation)
>  "ruby" =3D~ /(?-v:perl)/  #=3D> false  (turn off negation)
>  "ruby" !~ /(?-v:perl)/  #=3D> true   (turn off negation)
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> The flag name "v" comes from the ex(1) command of the same name.
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> This has beneficial applications where it is sometimes difficult
> to construct what you want to match but much easier to construct
> what you *do not* want to match.  Having this negation built in
> the regexp itself would remove the need for us to change our=20
> Ruby code to process a regexp in a different way. =20
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> For example, suppose that you are passing a regexp to the `--name`
> command-line option of MiniTest.  This regexp tells MiniTest to
> only run those tests whose names match.  If Ruby had a negation
> flag on its regexps, then it would be suddenly trivial to make
> MiniTest skip certain tests by negating the regexp we pass in.
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> In this manner, we get a beneficial feature without ever changing
> our Ruby code (the codebase of MiniTest in this example).  :-)
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> Thanks for your consideration.
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> --=20
> http://redmine.ruby-lang.org
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