develooper Front page | perl.perl5.porters | Postings from July 2014

Re: New feature proposal : <<>> to disable magic open of ARGV

Thread Previous | Thread Next
July 27, 2014 09:04
Re: New feature proposal : <<>> to disable magic open of ARGV
Message ID:
Rafael Garcia-Suarez writes:

> On 27 July 2014 01:16, Ricardo Signes <> wrote:
> > To me, the most significant concern is probably the one about
> > improving our defaults.  I'm not sure I think this is the best
> > solution, but let me know if you think it's clearly better or worse,
> > or if it suggests anything else to you:
> >
> > * use feature 'magic_open_argv'
> > * ...which goes into the default feature bundle, and old versions
> > * ...but not the new version's bundle, so it's off by default on use 5.22
> > * ...and it's on in the while() code generated by -n
> > * ...but we have -N and -P
> Why the double negation?

This way, the only double negative is in Rik's description of the plan.
From a Perl programmer's point of view, it's simply that somebody
wanting to use the feature use-s it.

> use feature 'nomagic_open_argv' should work similarly.

But that imposes the double negative on users. In that if in perl 5.22
nomagic_open_argv is the default, somebody wanting the magic behaviour
would have to do:

  no feature qw<nomagic_open_argv>;

That's unquestionably a double negative, and is far harder to grok than:

  use feature qw<magic_open_argv>;

It also prevents bundling all the features you want into a single call.
Instead of:

  use feature qw<say magic_open_argv unicode_strings signatures>;

You'd have to write:

  use feature qw<say unicode_strings signatures>;
  no feature qw<nomagic_open_argv>;

It'd be a weird exception that most features are enabled positively but
one of them is enabled by disabling its opposite — an exception that's
only explained by historical reasons.

So I think nomagic_open_argv is much worse from the point of view of not
avoiding banishing double negatives ...

Girls don't wear their shoes out, and boys don't care about style?
  Clarks think so:
Disagree? Don't want shops promoting gender stereotypes to children?
  Please sign the petition:

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