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Rename nonbacktracking subexpression to atomic group#16980

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Thraka merged 4 commits intodotnet:masterfrom
danmoseley:atomic
Feb 10, 2020
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Rename nonbacktracking subexpression to atomic group#16980
Thraka merged 4 commits intodotnet:masterfrom
danmoseley:atomic

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@danmoseley danmoseley commented Feb 5, 2020

We currently call the (?>...) construction a "Nonbacktracking (or "greedy") subexpression."

As pointed out by @stephentoub , it is a use of greedy that is not standard. The standard term seems to be atomic group, with some variation eg atomic subexpression, once-only subpattern (PHP) etc.

Changed to atomic group throughout with acknowledgement in one location of the alternative terms.

BTW it feels like subexpression and nonbacktracking ought to have hyphens, but I'm not changing that here.

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@danmoseley danmoseley requested a review from Thraka as a code owner February 5, 2020 00:01
@dotnet-bot dotnet-bot added this to the February 2020 milestone Feb 5, 2020
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danmoseley commented Feb 5, 2020

PHP - once only subpattern: https://www.php.net/manual/en/regexp.reference.onlyonce.php
Regexegg: atomic group https://www.rexegg.com/regex-disambiguation.html
Regularexpressions-info: atomic group https://www.regular-expressions.info/atomic.html
Boost : independent sub-expressions https://www.boost.org/doc/libs/1_44_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html
RE2: possessive match (but given its nature doesn't need them) https://github.com/google/re2/wiki/Syntax
Ruby: atomic group: https://ruby-doc.org/core-2.7.0/Regexp.html
PCRE: atomic group http://www.pcre.org/pcre2.txt

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stephentoub commented Feb 5, 2020 •
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cc: @CyrusNajmabadi

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CyrusNajmabadi commented Feb 5, 2020

thnks! i can make the roslyn change when this goes in.

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stephentoub reviewed Feb 5, 2020
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stephentoub reviewed Feb 5, 2020
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stephentoub commented Feb 5, 2020

Thanks for updating this, @danmosemsft.

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danmoseley commented Feb 5, 2020

Feedback addressed

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danmoseley commented Feb 8, 2020

@Thraka does this look good to merge?

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Thraka approved these changes Feb 10, 2020
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LGTM!

@Thraka Thraka merged commit 91550cf into dotnet:master Feb 10, 2020
@CyrusNajmabadi CyrusNajmabadi mentioned this pull request Feb 10, 2020
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