develooper Front page | perl.perl5.porters | Postings from January 2012

Re: How we deprecate (was Re: Deprecating '\w {' in v5.16)

Thread Previous | Thread Next
January 30, 2012 22:31
Re: How we deprecate (was Re: Deprecating '\w {' in v5.16)
Message ID:
Karl Williamson <> wrote:
:On 01/30/2012 10:18 AM, Karl Williamson wrote:
:> On 01/30/2012 01:06 AM, wrote:
:>> I consider this deprecation risky: it may break things by being
:>> misimplemented, or it may break things by introducing new warnings deep
:>> in code that doesn't expect it. Further, I consider there is a non-zero
:>> probability that once we try it we may find that the practice we wish
:>> to deprecate is so widespread that we reconsider our approach.
:>> In particular, this isn't some practice that was previously dubious or
:>> "always broken" - as far as I know, the norm and received wisdom has
:>> always been "don't escape what doesn't require it".
:>> Attempting this at the start of a cycle would give us the space we need
:>> to discover whether it's a really bad idea.
:> It's not clear to me if you are referring to just the more general
:> proposal to deprecate all unescaped left braces; or the more restricted
:> one to deprecate those in a backslash-alpha-brace sequence.

I think the argument applies to both, to different degrees.

:> The former has already been marked as contentious, so will not go into
:> 5.16. If the latter, then it too can not be implemented in 5.16.
:BTW, one advantage of doing either of these is that people have 
:complained, and their may be tickets open on (don't have time just now 
:to check) that if they make a typo in a {quantifier}, there's no 
:message.  Now there would be, and we could close any of those tickets

I agree the current system is suboptimally sane, and I have wished for
at least the last 5 years that it had been designed slightly more
restrictively from the start.

The question is, I guess, what is the cost/benefit analysis of changing
it now. I think we have a reasonable idea of the benefit, but so far all
the information I've seen about the cost is the results of that one test
run of perl itself - and that seemed pretty bad.


Thread Previous | Thread Next Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About