[ruby-core:94610] [Ruby master Feature#16120] Omitted block argument if block starts with dot-method call

Issue #16120 has been updated by Dan0042 (Daniel DeLorme).

Description updated
Subject changed from Implicit block argument if block starts with dot-method call to Omitted block argument if block starts with dot-method call

@nobu, wow, thank you so much. I never imagined it would be THAT simple to implement.
`O_O  @_@  m(_ _)m`

But I do think it would be better with `(parser_numbered_param(p, 0))` in the commit [here](https://github.com/ruby/ruby/commit/7d14171d959f4088b04ca892cb36472171fa01e9) `m(_ _)m`

---

jeremyevans0 (Jeremy Evans) wrote:
> In the cases it does handle, it does save a character compared to the implicit parameter approach.  I don't think that character saving makes the code clearer than the single implicit parameter approach, though.  In my opinion they are even in terms of clarity.

I totally agree that "saving" a single character makes no difference. But all these proposals are not about reducing mere character count, they're about reducing... I don't know the right word... cognitive complexity? lexical redundancy? conceptual overhead? It's the reason why people propose `{item.foo}` even though it has *zero* characters less than `{|x|x.foo}`. It's the reason why people who use nice descritive variable and method names can also propose `{@.foo}` even though it's an insignificant three character saving. It's the reason why human languages use omissions and pronouns. Allow me to make a comparison with english:

```
omitted   {.foo}      John went to the market and bought apples
implicit  {@.foo}     John went to the market and he bought apples
explicit  {|x|x.foo}  John went to the market and John bought apples
```

There's a reason why the first form is the most natural. When people talk about a block shorthand, I really think they mean shorter in the sense of cognition, not character count (although the two are somewhat related). So rather than thinking of a 1-char saving, it's more like explicit has 2x overhead, implicit has 1x, and omitted has 0x. Yes, we're talking about a very very tiny amount of overhead, I'll grant you, but enough to have these proposals keep popping up. That's not to say the implicit parameter approach is bad, in fact I rather like it. I just happen to think the omitted approach has so much better "flow". 1x/0x = Infinity kind of thing.


> I think the implicit parameter approach (`{JSON.parse(@)}`) is a simpler and more readable approach than the dot-colon approach (`(&JSON.:parse)`).

I totally agree there again. I was trying to present the perspective of functional-style first-class-function people (which I am not). Maybe trying to argue on behalf of others is a mistake in itself.

----------------------------------------
Feature #16120: Omitted block argument if block starts with dot-method call
https://bugs.ruby-lang.org/issues/16120#change-81086

* Author: Dan0042 (Daniel DeLorme)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
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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