Sorry for being think but what is
say (:?foo);
meant to do? The OP just says it should "work".
On Sun, Jul 23, 2017 at 6:05 AM Aleks-Daniel Jakimenko-Aleksejev via RT <
perl6-bugs-follo...@perl.org> wrote:
> sub foo($bar!) { say $bar }; foo(42)
>
> On 2017-07-22 11:19:41, alex.jakime...@gmail.com wrote:
> > Eh. The effort required to implement the feature is much less than
> > having
> > discussions *like this*. I'll try to be quick.
> >
> > “there's large possibility of introducing some unwanted ambiguity
> > somewhere”
> >
> > A good thing to keep in mind indeed.
> >
> > I don't really like these discussions before actual PRs, but if we
> > think about
> > it a little bit…
> >
> > <colonpair> panics if it finds :! but then fails to find <identifier>
> > (
> >
>
> https://github.com/rakudo/rakudo/blob/fb7ecb60f006b5738bfe7a234535e07344268b31/src/Perl6/Grammar.nqp#L1892
> > ), so if there is any ambiguity introduced, then it's not bigger than
> > what we
> > have with :! already.
> >
> > I've tried ::!CLASS and it complains about private method !CLASS.
> >
> > :?foo itself says “Confused … expecting any of: colon pair”, so it
> > expects a
> > colon pair anyway.
> >
> > Maybe you have some good examples, but *so far* looks ok.
> >
> >
> > “complex syntax feature”
> >
> > Let's make this complex feature strangely consistent.
> >
> >
> > “OP came up[^1] with this idea while trying to think of more cases to
> > add to
> > the catalog of colon uses in Rakudo”
> >
> > Why does this sound so bad? :) Does it really matter at what point I
> > noticed
> > that the feature that I always thought was implemented actually isn't?
> > I don't
> > use colonpairs as often, truthy or falsy, so never noticed before.
> >
> > However, even the fact that :!foo does not align vertically with :bar
> > is enough
> > to convince me regarding the usefulness of the proposed feature.
> >
> >
> > “But if we follow that logic, it'd mean:”
> >
> > What I meant was that we can make it strangely consistent in a useful
> > way. Then
> > you extrapolated it to unbelievable extents.
> >
> > Then there are examples that are totally unrelated to the ticket. Even
> > ?? !! is
> > not in any way strangely consistent (you can't write else { } if { }).
> >
> >
> > I like this definition a lot:
> >
> > <masak> "strangely consistent" is all about using loose connections
> > people have
> > in their brains, so that a feature feels syntactically vaguely right
> > for
> > various reasons.
> >
> >
> > This ticket is not about making colonpairs accept prefix operators. It
> > is also
> > not about being able to syntactically put ? anywhere you can put !.
> > And let's
> > also not bring unrelated stuff here (like colonpairs only accepting
> > natural
> > numbers with *no sign* whatsoever). What kind of derailing kung fu is
> > this
> > anyway?
> >
> >
> > On 2017-07-22 09:12:31, c...@zoffix.com wrote:
> > > On Sat, 22 Jul 2017 07:53:26 -0700, alex.jakime...@gmail.com wrote:
> > > > This should work:
> > > >
> > > > Code:
> > > > say (:?foo);
> > > >
> > > > Result:
> > > > ===SORRY!=== Error while compiling -e
> > > > Bogus statement
> > > > at -e:1
> > > > ------> say (:⏏?foo);
> > > > expecting any of:
> > > > colon pair
> > > >
> > > >
> > > > Because these work:
> > > >
> > > > Code:
> > > > say (:foo);
> > > > say (:!foo);
> > > >
> > > > Result:
> > > > foo => True
> > > > foo => False
> > >
> > >
> > > -1 from me:
> > >
> > > 1) Colonpairs are ubiquitous in the language, so there's large
> > > possibility of introducing some unwanted ambiguity somewhere and it's
> > > hard to predict where it might occur
> > > 2) Colonpairs are already one of the most complex syntax feature of
> > > the language, requiring beginners to learn a wealth of syntax to
> > > understand most of the common code.
> > > 3) Given (1) and (2), I'd expect any changes to extend their syntax
> > > to
> > > carry large benefits, however, the proposal offers literally zero
> > > practical use and the OP came up[^1] with this idea while trying to
> > > think of more cases to add to the catalog of colon uses in Rakudo.
> > > The
> > > `?` prefix op at least coerces the already-true arg to Bool (e.g.
> > > `?"foo" === True`) but in the case of the colonpair, there's nothing
> > > to coerce, so there's absolutely no point in typing the extra `?` and
> > > it's unlikely anyone would want to type it.
> > > 4) The OP makes the case that this syntax should exist solely for the
> > > sake of consistency, by interpreting the `!` in `:!foo` syntax to
> > > mean
> > > the `!` op, and there exists the `?` op. But if we follow that logic,
> > > it'd mean:
> > > *) `!! ??` should be allowed too, to mean reverse ternary
> > > *) `::!CLASS` should mean `anything but ::?CLASS`
> > > *) `has $?foo` should be an alternative to `has $!foo`
> > > *) `self?foo` should be an alternative to `self!foo`
> > > *) `:-42foo` should parse just as `:42foo` parses
> > > The point being that the current syntax is `":"` vs `":!"` not `":"`
> > > vs `":" + some op`. And things that have "!" in them do not
> > > necessarily need to have a "?" alternative.
> > >
> > > In summation, there's no practical use of this feature and it is
> > > unlikely it'll ever be used in real programs. The colonpair syntax is
> > > used across the entire language and any changes to it have large
> > > impact. It's very hard to anticipate any problematic ambiguity cases
> > > introduction of `?` into colon syntax might have. And given lack of
> > > technical benefits of this feature, I do not think we should accept
> > > the risks.
> > >
> > >
> > > [1] https://irclog.perlgeek.de/perl6/2017-07-22#i_14907647
>
