Issue #15723 has been updated by jeremyevans0 (Jeremy Evans).


Marc,

Thank you for your analysis, I think you have raised a number of good points.

marcandre (Marc-Andre Lafortune) wrote:
> Let's first agree that a shorthand notation would only simplify `{|x| foo(x) }` and no other block signature.

I agree that a shorter notation for `{|x|}` instead of `{|x,|}` would be beneficial.  That does not imply that that a shorthand for `{|x,y|}` is not useful (e.g. `{@1 + @2}`), though I think it is definitely less useful.

> Then we can discuss if it should be `@1`, `@`, `it`, or my personal favorite (that I havn't seen discussed): `_`.

My original proposal was `@` for a single block argument, and `@1` and `@2` for multiple block arguments as a possible extension.  It may make sense to have `{@}` means `{|x| x}` and `{@1 + @2}` means `{|x,y| x + y}`.  We would want to disallow mixing `@` and `@1`/`@2` in that case, and maybe we should consider disallowing `@1` without `@2` or some higher number, since the actual desire for `{|x,|}` behavior is probably limited.

As for `it` and `_`, both are not backwards compatible as they are valid local variables:

```ruby
it = 1
_ = 2
lambda{it}.call
# => 1
lambda{_}.call
# => 2
```

----------------------------------------
Misc #15723: Reconsider numbered parameters
https://bugs.ruby-lang.org/issues/15723#change-77487

* Author: sos4nt (Stefan Schler)
* 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: <mailto:ruby-core-request / ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>