[ruby-core:94612] [Ruby master Feature#16120] Omitted block argument if block starts with dot-method call

[hanmac@gmx.de]

Issue #16120 has been updated by Hanmac (Hans Mackowiak).


@Dan0042 in your list about implicit and explicit you forgot `{ foo }` depending on the method who gets the block, it might does an instance_eval thing where the block self is the block variable

i know that would need to change of the method, but this one might be possible too

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Feature #16120: Omitted block argument if block starts with dot-method call
https://bugs.ruby-lang.org/issues/16120#change-81088

* Author: Dan0042 (Daniel DeLorme)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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How about considering this syntax for implicit block parameter:
```
[10, 20, 30].map{ .to_s(16) }  #=> ["a", "14", "1e"]
```
Infinite thanks to @maedi for [the idea](https://bugs.ruby-lang.org/issues/15723#note-19)

This proposal is related to #4475, #9076, #10829, #12115, #15302, #15483, #15723, #15799, #15897, #16113 (and probably many others) which I feel are all trying to solve the same "problem". So I strongly believe all these feature requests should to be considered together in order to make a decision.

This "problem" can be more-or-less stated thus:
* There is a very common pattern in ruby: `posts.map{ |post| post.author.name }`
* In that line, the three 3 "post" in close proximity feel redundant and not DRY.
* To reduce the verbosity, people tend to use a meaningless one-character variable in the block
* But even so `posts.map{ |p| p.author.name }` still feels redundant.
* This "problem" is felt by many in the ruby community, and is the reason people often prefer `posts.map(&:author)`
* But that only works for one method with no arguments.
* This results in many requests for a block shorthand than can do more.

I realize that many people feel this is not a problem at all and keep saying "just use regular block syntax". But the repeated requests over the years, as well as the widespread usage of `(&:to_s)`, definitely indicate this is a wish/need for a lot of people.

Rather than adding to #15723 or #15897, I chose to make this a separate proposal because, unlike `it` or `@` implicit variables, it allows to simplify **only** `{ |x| x.foo }`, not `{ |x| foo(x) }`. This is on purpose and, in my opinion, a desirable limitation.

The advantages are (all in my opinion, of course)
* Extremely readable: `posts.map{ .author.name }`
   * Possibly even more than with an explicit variable.
* Of all proposals this handles the most important use-case with the most elegant syntax.
   * It's better to have a beautiful shorthand for 90% of cases than a non-beautiful shorthand for 100% of cases.
   * A shorthand notation is less needed for `{ |x| foo(x) }` since the two `x` variables are further apart and don't feel so redundant.
* No ascii soup
* No potential incompatibility like `_` or `it` or `item`
* Very simple to implement; there's just an implicit `|var| var` at the beginning of the block.
* In a way it's similar to chaining methods on multiple lines:

        posts.map{ |post| post
          .author.name
        }

It may be interesting to consider that the various proposals are not *necessarily* mutually exclusive. You *could* have `[1,2,3].map{ .itself + @ + @1 }`. Theoretically.

I feel like I've wanted something like this for most of the 16 years I've been coding ruby. Like... **this** is what I wanted that `(&:to_s)` could only deliver half-way. I predict that if this syntax is accepted, most people using `(&:to_s)` will switch to this.




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