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
