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Feature #16120

Omitted block argument if block starts with dot-method call

Added by Dan0042 (Daniel DeLorme) about 1 year ago. Updated about 1 year ago.

Status:
Rejected
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:94503]

Description

How about considering this syntax for implicit block parameter:

[10, 20, 30].map{ .to_s(16) }  #=> ["a", "14", "1e"]

Infinite thanks to maedi (Maedi Prichard) for the idea

This proposal is related to #4475, #8987, #9076, #10318, #10394, #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. And then closed together.

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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