in reply to Re^6: about style: use possessive or atomic?
in thread about style: use possessive or atomic?

> Is the warning erroneous?

if the meaning of {n}+ hasn't be deprecated or changed its a totally wrong warning.

Please run my code with 5.20, with same results we should file a bug report.

edit

As you can see there its not redundant.

The plus is neither a greedyness operator here, bc its in second place, its there to stop backtracking.

update
Apparently adding the second + turns the whole quantifier {n}+ into a possessive quantifier.

see here

Like a greedy quantifier, a possessive quantifier repeats the token as many times as possible. Unlike a greedy quantifier, it does not give up matches as the engine backtracks. With a possessive quantifier, the deal is all or nothing. You can make a quantifier possessive by placing an extra + after it. * is greedy, *? is lazy, and *+ is possessive. ++, ?+ and {n,m}+ are all possessive as well.

so + is "greedy" and ++ "possessive", {n}+ is analogous to ++ .

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!

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Re^8: about style: use possessive or atomic? (BUG!!!)
by LanX (Saint) on Aug 16, 2015 at 22:58 UTC
    so I installed 5.20.2 via perlbrew and it's even getting scarier, the behaviour of {n}+ has changed.

      DB<3> print "aaa" =~ /(a+){1}+a/
aa
  DB<4> print "aaa" =~ /(a+){1}a/     
aa
  DB<5> print $]
5.020002

    [download]

    while with 5.14 it's still like documented:

      DB<1> print "aaa" =~ /(a+){1}+a/

  DB<2> print "aaa" =~ /(a+){1}a/
aa
  DB<3> print $]
5.014002

    [download]

    This is worse than an erroneous warning that's a fatal break of backwards compatibility!

    update

    5.20 is backtracking while told otherwise

    Read more... (2 kB)

    And that's the trace from 5.14

    Read more... (4 kB)

    Cheers Rolf
    (addicted to the Perl Programming Language and ☆☆☆☆ :)
    Je suis Charlie!

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      So I think that you can post it to perlbug with a link to this node?
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