[#100689] [Ruby master Feature#17303] Make webrick to bundled gems or remove from stdlib — hsbt@...
Issue #17303 has been reported by hsbt (Hiroshi SHIBATA).
11 messages
2020/11/02
[#100852] [Ruby master Feature#17326] Add Kernel#must! to the standard library — zimmerman.jake@...
SXNzdWUgIzE3MzI2IGhhcyBiZWVuIHJlcG9ydGVkIGJ5IGpleiAoSmFrZSBaaW1tZXJtYW4pLg0K
24 messages
2020/11/14
[#100930] [Ruby master Feature#17333] Enumerable#many? — masafumi.o1988@...
Issue #17333 has been reported by okuramasafumi (Masafumi OKURA).
10 messages
2020/11/18
[#101071] [Ruby master Feature#17342] Hash#fetch_set — hunter_spawn@...
Issue #17342 has been reported by MaxLap (Maxime Lapointe).
26 messages
2020/11/25
[ruby-core:100848] [Ruby master Feature#14781] Enumerator.generate
From:
zverok.offline@...
Date:
2020-11-14 21:34:47 UTC
List:
ruby-core #100848
Issue #14781 has been updated by zverok (Victor Shepelev).
@chrisseaton I do!
Everything that is good for the community is good by me.
----------------------------------------
Feature #14781: Enumerator.generate
https://bugs.ruby-lang.org/issues/14781#change-88490
* Author: zverok (Victor Shepelev)
* Status: Closed
* Priority: Normal
----------------------------------------
This is alternative proposal to `Object#enumerate` (#14423), which was considered by many as a good idea, but with unsure naming and too radical (`Object` extension). This one is _less_ radical, and, at the same time, more powerful.
**Synopsys**:
* `Enumerator.generate(initial, &block)`: produces infinite sequence where each next element is calculated by applying block to previous; `initial` is first sequence element;
* `Enumerator.generate(&block)`: the same; first element of sequence is a result of calling the block with no args.
This method allows to produce enumerators replacing a lot of common `while` and `loop` cycles in the same way `#each` replaces `for`.
**Examples:**
With initial value
```ruby
# Infinite sequence
p Enumerator.generate(1, &:succ).take(5)
# => [1, 2, 3, 4, 5]
# Easy Fibonacci
p Enumerator.generate([0, 1]) { |f0, f1| [f1, f0 + f1] }.take(10).map(&:first)
#=> [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
require 'date'
# Find next Tuesday
p Enumerator.generate(Date.today, &:succ).detect { |d| d.wday == 2 }
# => #<Date: 2018-05-22 ((2458261j,0s,0n),+0s,2299161j)>
# Tree navigation
# ---------------
require 'nokogiri'
require 'open-uri'
# Find some element on page, then make list of all parents
p Nokogiri::HTML(open('https://www.ruby-lang.org/en/'))
.at('a:contains("Ruby 2.2.10 Released")')
.yield_self { |a| Enumerator.generate(a, &:parent) }
.take_while { |node| node.respond_to?(:parent) }
.map(&:name)
# => ["a", "h3", "div", "div", "div", "div", "div", "div", "body", "html"]
# Pagination
# ----------
require 'octokit'
Octokit.stargazers('rails/rails')
# ^ this method returned just an array, but have set `.last_response` to full response, with data
# and pagination. So now we can do this:
p Enumerator.generate(Octokit.last_response) { |response|
response.rels[:next].get # pagination: `get` fetches next Response
}
.first(3) # take just 3 pages of stargazers
.flat_map(&:data) # `data` is parsed response content (stargazers themselves)
.map { |h| h[:login] }
# => ["wycats", "brynary", "macournoyer", "topfunky", "tomtt", "jamesgolick", ...
```
Without initial value
```ruby
# Random search
target = 7
p Enumerator.generate { rand(10) }.take_while { |i| i != target }.to_a
# => [0, 6, 3, 5,....]
# External while condition
require 'strscan'
scanner = StringScanner.new('7+38/6')
p Enumerator.generate { scanner.scan(%r{\d+|[-+*/]}) }.slice_after { scanner.eos? }.first
# => ["7", "+", "38", "/", "6"]
# Potential message loop system:
Enumerator.generate { Message.receive }.take_while { |msg| msg != :exit }
```
**Reference implementation**: https://github.com/zverok/enumerator_generate
I want to **thank** all peers that participated in the discussion here, on Twitter and Reddit.
---Files--------------------------------
enumerator_from.rb (3.16 KB)
enumerator-generate.patch (4.44 KB)
0001-Implement-Enumerator.produce-Feature-14781.patch (4.47 KB)
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