I wouldn't be so eager to judge the proposal based on the original post.
Sometimes I submit tickets fast, and sometimes ideas are not conveyed as
clearly as I assumed.
“How are those things related?”
These were the examples of the pair syntax (what works and what doesn't). Now,
?↔! pattern is strangely established by at least two precedents:
* ? and ! prefix ops (e.g. !42 or ?42)
* Optional and required parameters (e.g. $foo?, $bar!, :$baz?, :$cat!)
Check out irc logs for more discussion.
On 2017-07-22 21:50:58, duff wrote:
> The OP said :?foo should work because :foo and :!foo work. I don't
> follow
> the logic. How are those things related? Why should :foo and :!foo
> imply
> :?foo? (In my head it makes as much sense as ":foo and :!foo implies
> :*foo", which is to say, none.)
>
> I don't see any benefit to adding a :?foo syntax that means exactly
> the
> same thing as :foo. I also don't see how it increases or improves
> consistency (strangely or otherwise). That it could be implemented
> quickly
> or easily is irrelevant.
>
> So ... -1 for me too.
>
> -Scott
>
>
> On Sat, Jul 22, 2017 at 10:11 PM, Lloyd Fournier via RT <
> perl6-bugs-follo...@perl.org> wrote:
>
> > 2¢:
> > ? doesn't imply truth it implies a question. The ? prefix asks an
> > expression whether it's True or False. When used as a sigil like
> > $?FILE
> > it's asking the compiler about something.
> >
> > ‘:foo’ sets foo to True. ‘:!foo’ sets it to False. ‘:?foo’ looks like
> > it's
> > trying to ask something a question, but I'm not sure about what.
> >
> > On Sun, Jul 23, 2017 at 12:41 PM Aleks-Daniel Jakimenko-Aleksejev via
> > RT <
> > perl6-bugs-follo...@perl.org> wrote:
> >
> > > Yes, I should have been more clear.
> > >
> > > Basically, it should work like (:foo) does, which is construct foo
> > > =>
> > True
> > > pair.
> > >
> > > On 2017-07-22 19:25:19, lloyd.fo...@gmail.com wrote:
> > > > Sorry for being think but what is
> > > > say (:?foo);
> > > > meant to do? The OP just says it should "work".
> > > >
> > > > On Sun, Jul 23, 2017 at 6:05 AM Aleks-Daniel Jakimenko-Aleksejev
> > > > via
> > > > RT <
> > > > perl6-bugs-follo...@perl.org> wrote:
> > > >
> > > > > sub foo($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/fb7ecb60f006b5738bfe7a234535e0
> > 7344268b31/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
> > > > >
> > >
> >
> >
