Issue #15723 has been updated by DarkWiiPlayer (Dennis Fischer).


I see many suggestions for different keywords or sigils, but they're all about the argument itself. What i feel is being ignored is adding to the block syntax itself; for example:

``` ruby
[1, 2, 3].map { a * a } # a has no special meaning here

[1, 2, 3].map ${ a * a } # a stands for the first argument here

# or

[1, 2, 3].map | arg_1 * arg_1 |
```

The second one looks like it could cause ambiguities with normal block arguments, but consider that those can only go at the start of a block, and blocks cannot go there anyway.

This would 1) keep old code compatible, 2) look nicer and 3) possibly make error messages clearer on older interpreters.

I also thing that specially the second example with the pipe characters would be nice, as pipes are already associated with block arguments.

The only downside I see is that pipes would make nested and multiline blocks very hard to read, but then again, I don't think numbered arguments should be used in those situations either.

----------------------------------------
Misc #15723: Reconsider numbered parameters
https://bugs.ruby-lang.org/issues/15723#change-79946

* Author: sos4nt (Stefan Schler)
* Status: Feedback
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
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.

---Files--------------------------------
implicit-param.diff (20 KB)


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