From: merch-redmine@... Date: 2019-04-12T21:11:19+00:00 Subject: [ruby-core:92264] [Ruby trunk Misc#15723] Reconsider numbered parameters Issue #15723 has been updated by jeremyevans0 (Jeremy Evans). Eregon (Benoit Daloze) wrote: > headius (Charles Nutter) wrote: > > Conflicts with bitwise AND, doesn't it? > > No, binary operators already care about spacing to clarify which one it is, and this syntax "conflict" already exists anyway: > > ~~~ ruby > irb(main):001:0> class Integer; def to_proc; -> x { x + self }; end; end > => :to_proc > irb(main):002:0> 2.then(&3) > => 5 > irb(main):003:0> 2.then &3 > => 5 > irb(main):004:0> 2.then & 3 > Traceback (most recent call last): > 4: from /home/eregon/.rubies/ruby-trunk/bin/irb:23:in `
' > 3: from /home/eregon/.rubies/ruby-trunk/bin/irb:23:in `load' > 2: from /home/eregon/prefix/ruby-trunk/lib/ruby/gems/2.7.0/gems/irb-1.0.0/exe/irb:11:in `' > 1: from (irb):4 > NoMethodError (undefined method `&' for #) > ~~~ > > We live fine with it so far, and I think it's fairly intuitive. The behavior changes if `foo` is a local variable: ```ruby foo = 1 proc{foo &1}.call # => 1 proc{foo & 1}.call # => 1 ``` This proposal has the following issue, where the same token (`&1`) could mean different things: ```ruby proc{&1.(&1)} ``` Is this: ```ruby proc{|x| x.call(x)} ``` or: ```ruby proc{|x| x.call(&(1.to_proc))} ``` `@1` has the advantage that such a syntax is not currently valid at any point, and therefore it does not cause backwards compatibility issues. I think using `&1` would cause problems, because any time you passed it as the last argument to a method, it would ambiguous as to whether you mean Integer#to_proc or the implicit block argument. ---------------------------------------- Misc #15723: Reconsider numbered parameters https://bugs.ruby-lang.org/issues/15723#change-77597 * Author: sos4nt (Stefan Sch����ler) * Status: Feedback * Priority: Normal * Assignee: ---------------------------------------- I just learned that *numbered parameters* have been merged into Ruby 2.7.0dev. For readers not familiar with this feature: it allows you to reference block arguments solely by their *index*, e.g. ```ruby [1, 2, 3].each { |i| puts i } # can become [1, 2, 3].each { puts @1 } ``` I have an issue with this new feature: I think **it encourages sloppy programming** and results in **hard to read code**. --- The [original proposal](https://bugs.ruby-lang.org/issues/4475) was to include a special variable (or keyword) with a **readable name**, something like: ```ruby [1, 2, 3].each { puts it } # or [1, 2, 3].each { puts this } ``` Granted, that looks quite lovely and it actually speaks to me ��� I can *understand* the code. And it fits Ruby: (quoting the website) > [Ruby] has an elegant syntax that is natural to read and easy to write. But the proposed `it` / `this` has limited application. It's only useful when dealing with a single argument. You can't have multiple `it`-s or `this`-es. That's why `@1`, `@2`, `@3` etc. were chosen instead. However, limiting the usefulness to a single argument isn't bad at at. In fact, a single argument seem to be the limit of what makes sense: ``` h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" } # vs h = Hash.new { @1[@2] = "Go Fish: #{@2}" } ``` Who wants to read the latter? That looks like an archaic bash program (no offense). We already discourage Perl style `$`-references: (from [The Ruby Style Guide](https://github.com/rubocop-hq/ruby-style-guide#no-perl-regexp-last-matchers)) > Don't use the cryptic Perl-legacy variables denoting last regexp group matches (`$1`, `$2`, etc). Use `Regexp.last_match(n)` instead. I don't see how our code can benefit from adding `@1` and `@2`. Naming a parameter isn't useless ��� it gives context. With more than one parameter, naming is crucial. And yes, naming is hard. But avoiding proper naming by using indices is the wrong way. So please reconsider numbered parameters. Use a readable named variable (or keyword) to refer to the first argument or ditch the feature entirely. -- https://bugs.ruby-lang.org/ Unsubscribe: