RFC: use feature 'vt_space' to add VT to \s.

Perl is the odd-man out in regards to handling the vertical tab, 
compared to Unicode, and other languages.  It presents more cognitive 
load on people to remember this exception.

I'm proposing in 5.16 to have 'use 5.016' cause \s to add VT to what it 
matches.

Some months ago Tom C asked Larry about why it wasn't;  the response was 
he couldn't remember, and had no objection to changing it now.
0
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11/21/2011 7:29:00 PM
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On Mon, Nov 21, 2011 at 12:29:00PM -0700, Karl Williamson wrote:
> Perl is the odd-man out in regards to handling the vertical tab, 
> compared to Unicode, and other languages.  It presents more cognitive 
> load on people to remember this exception.

> Some months ago Tom C asked Larry about why it wasn't;  the response was 
> he couldn't remember, and had no objection to changing it now.

I don't know the direct history, but I know that Perl predates ANSI C.
Ken Thompson's "On Trusting Trust" explains how one would add \v to the
C compiler - was \v a "late" addition to C's escapes?

If so, would that imply that Perl standardised its escapes earlier than C?

And yes, it bugs me every so often that \v is not there.

I don't have a confident opinion on whether this is the best way to address
that.

Nicholas Clark
0
nick
11/21/2011 7:47:36 PM
On 11/21/2011 12:47 PM, Nicholas Clark wrote:
> was \v a "late" addition to C's escapes?

It's not in my 1st edition 1978 K&R, but is in the 2nd edition 1988.

The same situation applies to \a, and \x for that matter
0
public
11/21/2011 8:10:34 PM
--3V7upXqbjpZ4EhLz
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* Karl Williamson <public@khwilliamson.com> [2011-11-21T14:29:00]
> Perl is the odd-man out in regards to handling the vertical tab,
> compared to Unicode, and other languages.  It presents more
> cognitive load on people to remember this exception.
>=20
> I'm proposing in 5.16 to have 'use 5.016' cause \s to add VT to what
> it matches.

What's the status of this?  I'm mid-compile of blead now, but as I recall it
did not happen, nor was it rallied against.

I'd be interested in seeing this done in early 5.17, possibly as a plain old
bug fix, to see what effects we see.  I don't think we need to rush it in n=
ow,
though.

--=20
rjbs

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0
perl
2/14/2012 5:04:05 AM
On 02/13/2012 10:04 PM, Ricardo Signes wrote:
> * Karl Williamson<public@khwilliamson.com>  [2011-11-21T14:29:00]
>> Perl is the odd-man out in regards to handling the vertical tab,
>> compared to Unicode, and other languages.  It presents more
>> cognitive load on people to remember this exception.
>>
>> I'm proposing in 5.16 to have 'use 5.016' cause \s to add VT to what
>> it matches.
>
> What's the status of this?  I'm mid-compile of blead now, but as I recall it
> did not happen, nor was it rallied against.
>
> I'd be interested in seeing this done in early 5.17, possibly as a plain old
> bug fix, to see what effects we see.  I don't think we need to rush it in now,
> though.
>

To do this without any backward compatibility issues would require a new 
feature to turn on and off, runtime checks, and another regex flag, so I 
didn't pursue it because it seemed like a big hassle for something that 
was such a small gain really.

If we decided to do this as a bug fix and not worry about backwards 
compatibility, that would be a lot easier; the hardest part would be 
changing the documentation.
0
public
2/14/2012 4:01:26 PM
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