Wishlist: (?(-1)yes-regexp) and (?(-2)yes-regexp|no-regexp)

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Migrated from rt.perl.org#86378 (status was 'open')

Searchable as RT86378$

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From g+i@gameintellect.com

Hello Jon Allen,

I found a bug in a format of the conditional expressions, see
http​://perldoc.perl.org/perlretut.html#Conditional-expressions

There are superfluous parentheses around a condition​:

(?(condition)yes-regexp) and (?(condition)yes-regexp|no-regexp)

because the conditions already have parentheses​:

(integer)
(?=...) etc.

The format of the conditional expression should be

(? condition yes-regexp) and (? condition yes-regexp|no-regexp)

By the way​: how about relative backreferences as a condition?
I think, it would be great, if we can use such conditional expressions​:

(?(-1)yes-regexp) and (?(-2)yes-regexp|no-regexp)

--
Regards
Serge

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From @briandfoy

In article <rt-3.6.HEAD-4136-1300351559-1942.86378-75-0@​perl.org>,
Serge <perlbug-followup@​perl.org> wrote​:

# New Ticket Created by Serge
# Please include the string​: [perl #86378]
# in the subject line of all future correspondence about this issue.
# <URL​: http​://rt.perl.org/rt3/Ticket/Display.html?id=86378 >

Hello Jon Allen,

I found a bug in a format of the conditional expressions, see
http​://perldoc.perl.org/perlretut.html#Conditional-expressions

There are superfluous parentheses around a condition​:

(?(condition)yes-regexp) and (?(condition)yes-regexp|no-regexp)

because the conditions already have parentheses​:

(integer)
(?=...) etc.

I think the current form is correct, and the part you think is odd is
explained in the sentence starting with "The second form is". I'd leave
the parens around "condition" to emphasize that some parens will be
there, no matter the source.

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The RT System itself - Status changed from 'new' to 'open'

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From @demerphq

On 18 March 2011 06​:41, brian d foy <brian.d.foy@​gmail.com> wrote​:

In article <rt-3.6.HEAD-4136-1300351559-1942.86378-75-0@​perl.org>,
Serge <perlbug-followup@​perl.org> wrote​:

# New Ticket Created by  Serge
# Please include the string​:  [perl #86378]
# in the subject line of all future correspondence about this issue.
# <URL​: http​://rt.perl.org/rt3/Ticket/Display.html?id=86378 >

Hello Jon Allen,

 I found a bug in a format of the conditional expressions, see
http​://perldoc.perl.org/perlretut.html#Conditional-expressions

 There are superfluous parentheses around a condition​:

(?(condition)yes-regexp) and (?(condition)yes-regexp|no-regexp)

because the conditions already have parentheses​:

(integer)
(?=...) etc.

I think the current form is correct, and the part you think is odd is
explained in the sentence starting with "The second form is". I'd leave
the parens around "condition" to emphasize that some parens will be
there, no matter the source.

I concur. The documentation is correct.

The prefix that denotes this construct is​:

(?(

The paren is NOT part of the condition, it is part of the regex syntax.

Yves

--
perl -Mre=debug -e "/just|another|perl|hacker/"

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From @doy

Closing.

-doy

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From [Unknown Contact. See original ticket]

Closing.

-doy

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@doy - Status changed from 'open' to 'resolved'

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From @cpansprout

On Tue Jul 03 18​:16​:04 2012, doy wrote​:

Closing.

I think you missed the fact that this ticket contains two separate
issues​: 1) the doc bug, which wasn’t a bug, and 2) a wishlist item​:
support for (?(-1)...).

The second has not been implemented or rejected.

--

Father Chrysostomos

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From [Unknown Contact. See original ticket]

On Tue Jul 03 18​:16​:04 2012, doy wrote​:

Closing.

I think you missed the fact that this ticket contains two separate
issues​: 1) the doc bug, which wasn’t a bug, and 2) a wishlist item​:
support for (?(-1)...).

The second has not been implemented or rejected.

--

Father Chrysostomos

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@doy - Status changed from 'resolved' to 'open'

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From @doy

On Tue, Jul 03, 2012 at 08​:35​:43PM -0700, Father Chrysostomos via RT wrote​:

On Tue Jul 03 18​:16​:04 2012, doy wrote​:

Closing.

I think you missed the fact that this ticket contains two separate
issues​: 1) the doc bug, which wasn’t a bug, and 2) a wishlist item​:
support for (?(-1)...).

The second has not been implemented or rejected.

Ah, I did miss that part, thanks.

-doy

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From @jkeenan

On Tue Jul 03 20​:39​:14 2012, doy@​tozt.net wrote​:

On Tue, Jul 03, 2012 at 08​:35​:43PM -0700, Father Chrysostomos via RT
wrote​:

On Tue Jul 03 18​:16​:04 2012, doy wrote​:

Closing.

I think you missed the fact that this ticket contains two separate
issues​: 1) the doc bug, which wasn’t a bug, and 2) a wishlist item​:
support for (?(-1)...).

The second has not been implemented or rejected.

Ah, I did miss that part, thanks.

-doy

When this ticket was originally opened in March 2011, the wishlist item
Father C refers to was​:

#####
By the way​: how about relative backreferences as a condition?
I think, it would be great, if we can use such conditional expressions​:

(?(-1)yes-regexp) and (?(-2)yes-regexp|no-regexp)
#####

No one has seconded the motion for this feature request in over two years.

Is there anyone who feels it ought to be implemented?

Is there anyone who is willing to take on the task of implementing it?

Thank you very much.
Jim Keenan

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From @cpansprout

On Sat Jun 29 17​:33​:57 2013, jkeenan wrote​:

On Tue Jul 03 20​:39​:14 2012, doy@​tozt.net wrote​:

On Tue, Jul 03, 2012 at 08​:35​:43PM -0700, Father Chrysostomos via RT
wrote​:

On Tue Jul 03 18​:16​:04 2012, doy wrote​:

Closing.

I think you missed the fact that this ticket contains two separate
issues​: 1) the doc bug, which wasn’t a bug, and 2) a wishlist item​:
support for (?(-1)...).

The second has not been implemented or rejected.

Ah, I did miss that part, thanks.

-doy

When this ticket was originally opened in March 2011, the wishlist item
Father C refers to was​:

#####
By the way​: how about relative backreferences as a condition?
I think, it would be great, if we can use such conditional expressions​:

(?(-1)yes-regexp) and (?(-2)yes-regexp|no-regexp)
#####

No one has seconded the motion for this feature request in over two years.

Is there anyone who feels it ought to be implemented?

Is there anyone who is willing to take on the task of implementing it?

Consider me willing, but also consider that it is at the bottom of by
list. :-)

I think it would be a very handy feature. Leaving it open keeps it on
the general to-do list.

--

Father Chrysostomos