From: hanmac@gmx.de
To: ruby-core@ruby-lang.org
Subject: [ruby-core:99045] [Ruby master Feature#16986] Anonymous Struct literal
Date: Fri, 03 Jul 2020 13:31:00 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-86421.20200703133100.17@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-16986.20200626065853.17@ruby-lang.org
Issue #16986 has been updated by Hanmac (Hans Mackowiak).
the problem i have with that is that each time it creates a (cached) struct class.
after taking so long to make frozen literals and making even such frozen objects GC able,
something that creates new (class) objects which then can never be cleared sounds like a problem that would bite you in the butt sooner or later
other than that, `Struct a: 1, b: 2` would probably be the most clean variant
----------------------------------------
Feature #16986: Anonymous Struct literal
https://bugs.ruby-lang.org/issues/16986#change-86421
* 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:[~2020-07-03 13:31 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 ` hanmac [this message]
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 ` [ruby-core:100225] " tenderlove
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
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