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


waheedi (Waheed Barghouthi) wrote:
> But why it can't be like this? `@[0]` I think its more clear, just saying.

If you mean that you would like the intended behavior to be:

```ruby
proc{@[0]}.call(1,2)
# => 1
```

You would only want this if you wanted to support multiple implicit block arguments, which is almost always going to result in code that is more difficult to understand, as referencing arguments by position instead of by name is problematic.  Only supporting a single implicit block argument makes the simple case simpler and in some cases clearer.

Even assuming you wanted to support multiple implicit block arguments, I responded earlier with some issues with using a single variable for that:

* You cannot calculate arity with a syntax that uses a single variable for all arguments.
* Requires 4 characters minimum to access an implicit variable.
* We should avoid adding syntax that requires allocating an array or any other object, as that is bad for performance.
* Any approach that used a single variable that was not a true object would be problematic.

Note that my proposal would support `@[0]`, but it would mean call the `[]` method on the first argument to the block with the value `0` (i.e. `@[0]` means `@.[](0)`).  Example:

```ruby
proc{@[0]}.call({0=>1})
# => 1

----------------------------------------
Misc #15723: Reconsider numbered parameters
https://bugs.ruby-lang.org/issues/15723#change-77662

* 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.



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