From: tenderlove@ruby-lang.org
To: ruby-core@ruby-lang.org
Subject: [ruby-core:100225] [Ruby master Feature#16986] Anonymous Struct literal
Date: Tue, 29 Sep 2020 20:27:55 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-87814.20200929202755.17@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-16986.20200626065853.17@ruby-lang.org
Issue #16986 has been updated by tenderlovemaking (Aaron Patterson).
marcandre (Marc-Andre Lafortune) wrote in #note-49:
> We could settle for `Struct.[]`:
>
> ```ruby
> Struct[name: 'Joe', id: 42] # => Struct.new(:name, :id, keyword_init: true).new(name: 'Joe', id: 42)
> ```
>
> No new syntax required. Less of cognitive load as it is a simple shortcut. A note in the doc that this won't be particularly performant and best reserved for test fakes or static constants.
I think that's pretty reasonable. `Struct.new.new` is not something I would do in a hot path. But maybe that's why we don't see more of it in library code? 🤷🏻♀️
----------------------------------------
Feature #16986: Anonymous Struct literal
https://bugs.ruby-lang.org/issues/16986#change-87814
* Author: ko1 (Koichi Sasada)
* Status: Open
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
----------------------------------------
# Abstract
How about introducing anonymous Struct literal such as `${a: 1, b: 2}`?
It is almost the same as `Struct.new(:a, :b).new(1, 2)`.
# Proposal
## Background
In many cases, people use hash objects to represent a set of values such as `person = {name: "ko1", country: 'Japan'}` and access its values through `person[:name]` and so on. It is not easy to write (three characters `[:]`!), and it easily introduces misspelling (`person[:nama]` doesn't raise an error).
If we make a `Struct` object by doing `Person = Struct.new(:name, :age)` and `person = Person.new('ko1', 'Japan')`, we can access its values through `person.name` naturally. However, it costs coding. And in some cases, we don't want to name the class (such as `Person`).
Using `OpenStruct` (`person = OpenStruct.new(name: "ko1", country: "Japan")`), we can access it through `person.name`, but we can extend the fields unintentionally, and the performance is not good.
Of course, we can define a class `Person` with attr_readers. But it takes several lines.
To summarize the needs:
* Easy to write
* Doesn't require declaring the class
* Accessible through `person.name` format
* Limited fields
* Better performance
## Idea
Introduce new literal syntax for an anonymous Struct such as: `${ a: 1, b: 2 }`.
Similar to Hash syntax (with labels), but with `$` prefix to distinguish.
Anonymous structs which have the same member in the same order share their class.
```ruby
s1 = ${a: 1, b: 2, c: 3}
s2 = ${a: 1, b: 2, c: 3}
assert s1 == s2
s3 = ${a: 1, c: 3, b: 2}
s4 = ${d: 4}
assert_equal false, s1 == s3
assert_equal false, s1 == s4
```
## Note
Unlike Hash literal syntax, this proposal only allows `label: expr` notation. No `${**h}` syntax.
This is because if we allow to splat a Hash, it can be a vulnerability by splatting outer-input Hash.
Thanks to this spec, we can specify anonymous Struct classes at compile time.
We don't need to find or create Struct classes at runtime.
## Implementatation
https://github.com/ruby/ruby/pull/3259
# Discussion
## Notation
Matz said he thought about `{|a: 1, b: 2 |}` syntax.
## Performance
Surprisingly, Hash is fast and Struct is slow.
```ruby
Benchmark.driver do |r|
r.prelude <<~PRELUDE
st = Struct.new(:a, :b).new(1, 2)
hs = {a: 1, b: 2}
class C
attr_reader :a, :b
def initialize() = (@a = 1; @b = 2)
end
ob = C.new
PRELUDE
r.report "ob.a"
r.report "hs[:a]"
r.report "st.a"
end
__END__
Warming up --------------------------------------
ob.a 38.100M i/s - 38.142M times in 1.001101s (26.25ns/i, 76clocks/i)
hs[:a] 37.845M i/s - 38.037M times in 1.005051s (26.42ns/i, 76clocks/i)
st.a 33.348M i/s - 33.612M times in 1.007904s (29.99ns/i, 87clocks/i)
Calculating -------------------------------------
ob.a 87.917M i/s - 114.300M times in 1.300085s (11.37ns/i, 33clocks/i)
hs[:a] 85.504M i/s - 113.536M times in 1.327850s (11.70ns/i, 33clocks/i)
st.a 61.337M i/s - 100.045M times in 1.631064s (16.30ns/i, 47clocks/i)
Comparison:
ob.a: 87917391.4 i/s
hs[:a]: 85503703.6 i/s - 1.03x slower
st.a: 61337463.3 i/s - 1.43x slower
```
I believe we can speed up `Struct` similarly to ivar accesses, so we can improve the performance.
BTW, OpenStruct (os.a) is slow.
```
Comparison:
hs[:a]: 92835317.7 i/s
ob.a: 85865849.5 i/s - 1.08x slower
st.a: 53480417.5 i/s - 1.74x slower
os.a: 12541267.7 i/s - 7.40x slower
```
For memory consumption, `Struct` is more lightweight because we don't need to keep the key names.
## Naming
If we name an anonymous class, literals with the same members share the name.
```ruby
s1 = ${a:1}
s2 = ${a:2}
p [s1, s2] #=> [#<struct a=1>, #<struct a=2>]
A = s1.class
p [s1, s2] #=> [#<struct A a=1>, #<struct A a=2>]
```
Maybe that is not a good behavior.
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2020-09-29 20:28 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-26 6:58 [ruby-core:98947] [Ruby master Feature#16986] Anonymous Struct literal ko1
2020-06-26 9:36 ` [ruby-core:98949] " shevegen
2020-06-26 10:09 ` [ruby-core:98951] " manga.osyo
2020-06-26 11:05 ` [ruby-core:98952] " zverok.offline
2020-06-26 11:08 ` [ruby-core:98953] " zverok.offline
2020-06-26 11:14 ` [ruby-core:98954] " jean.boussier
2020-06-26 11:15 ` [ruby-core:98955] " jean.boussier
2020-06-26 16:22 ` [ruby-core:98961] " zverok.offline
2020-06-27 12:37 ` [ruby-core:98981] " info+ruby
2020-06-27 14:28 ` [ruby-core:98982] " brooke
2020-06-27 17:55 ` [ruby-core:98985] " ko1
2020-06-27 18:08 ` [ruby-core:98986] " ko1
2020-06-27 18:31 ` [ruby-core:98987] " josef.simanek
2020-07-02 8:44 ` [ruby-core:99027] " hanmac
2020-07-02 11:34 ` [ruby-core:99028] " gabriel.sobrinho
2020-07-02 16:06 ` [ruby-core:99030] " caleb
2020-07-02 17:02 ` [ruby-core:99035] " jean.boussier
2020-07-02 18:58 ` [ruby-core:99037] " ko1
2020-07-02 20:56 ` [ruby-core:99039] " marcandre-ruby-core
2020-07-02 23:14 ` [ruby-core:99041] " dimasamodurov
2020-07-03 10:52 ` [ruby-core:99043] " esquinas.enrique
2020-07-03 13:31 ` [ruby-core:99045] " hanmac
2020-07-07 15:07 ` [ruby-core:99076] " jonathan
2020-07-10 8:16 ` [ruby-core:99109] " lgemon
2020-08-04 0:40 ` [ruby-core:99470] " ko1
2020-08-12 17:56 ` [ruby-core:99571] " masafumi.o1988
2020-08-12 19:48 ` [ruby-core:99573] " manga.osyo
2020-08-13 5:56 ` [ruby-core:99575] " nobu
2020-08-14 5:17 ` [ruby-core:99587] " masafumi.o1988
2020-08-17 6:09 ` [ruby-core:99606] " nobu
2020-08-17 7:16 ` [ruby-core:99607] " sawadatsuyoshi
2020-08-18 17:05 ` [ruby-core:99629] " esquinas.enrique
2020-08-19 19:05 ` [ruby-core:99648] " ko1
2020-08-20 14:48 ` [ruby-core:99660] " esquinas.enrique
2020-08-21 8:51 ` [ruby-core:99661] " mame
2020-08-24 3:13 ` [ruby-core:99676] " daniel
2020-08-24 13:43 ` [ruby-core:99682] " mame
2020-08-27 0:13 ` [ruby-core:99717] " ko1
2020-08-30 10:46 ` [ruby-core:99777] " nobu
2020-09-02 12:17 ` [ruby-core:99836] " duerst
2020-09-02 17:21 ` [ruby-core:99847] " marcandre-ruby-core
2020-09-03 1:32 ` [ruby-core:99860] " duerst
2020-09-28 19:37 ` [ruby-core:100203] " chris
2020-09-28 20:57 ` [ruby-core:100204] " marcandre-ruby-core
2020-09-29 14:35 ` [ruby-core:100215] " esquinas.enrique
2020-09-29 15:57 ` [ruby-core:100218] " marcandre-ruby-core
2020-09-29 16:15 ` [ruby-core:100219] " tenderlove
2020-09-29 17:15 ` [ruby-core:100222] " marcandre-ruby-core
2020-09-29 20:27 ` tenderlove [this message]
2020-09-30 1:36 ` [ruby-core:100226] " mame
2020-09-30 1:47 ` [ruby-core:100227] " marcandre-ruby-core
2020-09-30 13:08 ` [ruby-core:100235] " eregontp
2020-10-15 15:27 ` [ruby-core:100405] " ko1
2020-10-15 16:40 ` [ruby-core:100406] " marcandre-ruby-core
2020-10-15 17:40 ` [ruby-core:100407] " ko1
2020-10-15 17:43 ` [ruby-core:100408] " ko1
2020-10-15 19:10 ` [ruby-core:100409] " eregontp
2020-12-14 20:19 ` [ruby-core:101451] " shannonskipper
2022-01-15 16:57 ` [ruby-core:107141] " briankung (Brian Kung)
2022-12-31 1:43 ` [ruby-core:111548] " Bumppoman (Brendon Stanton) via ruby-core
2022-12-31 2:04 ` [ruby-core:111549] " matz (Yukihiro Matsumoto) via ruby-core
2022-12-31 17:52 ` [ruby-core:111555] " Eustáquio Rangel via ruby-core
2022-12-31 7:04 ` [ruby-core:111550] " shyouhei (Shyouhei Urabe) via ruby-core
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-list from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.ruby-lang.org/en/community/mailing-lists/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=redmine.journal-87814.20200929202755.17@ruby-lang.org \
--to=ruby-core@ruby-lang.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).