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
