Feature #14476
Updated by sawa (Tsuyoshi Sawada) over 3 years ago
In this issue, I propose to introduce `same_all?` instance method of `Array` class. This new method checks whether the all items in the receiver are the same. Today, I needed to write a the code to judge whether all items in an `Array` Array are the same. I wanted to make the following expression, which that I've written at first, more efficient. efficiently. ```ruby ary.all? {|e| e.foo == ary[0].foo } ``` I considered about thought the following another simpler case, too. ```ruby ary.all? {|e| e == ary[0] } ``` As I discussed with some CRuby committers and my colleagues at Speee, Inc., I found that both cases can be written more efficiently as follows: have the following efficient expressions: ```ruby # for the 1st case ary.empty? || ary[0].foo.yield_self {|e0| ary[1..-1].all? {|e| e.foo == e0 } } # for the 2nd case ary.empty? || ary[0..-2] == ary[1..-1] ``` However, it is not Both expressions aren't easy to understand the intent of either expression, which original purpose that is to check checking whether all the items are the same. I want to give this feature a clear name to make the code readable. And I think it should be provided as a core feature because it can be made more efficient by being implemented implementing in C language. The benchmark script is: https://gist.github.com/mrkn/26a0fcfc431a45fe809fbbef95aceaf5 I used it to find the efficient expressions. The example result of this benchmark on my MacBook Pro is here. ``` $ ruby -v bench.rb ruby 2.6.0dev (2018-02-14 trunk 62402) [x86_64-darwin16] ---------------------------------------- Benchmark case: shuffle user system total real all?-method-1 0.001525 0.000088 0.001613 ( 0.001632) all?-method-2 0.000489 0.000031 0.000520 ( 0.000565) all?-method-3 0.000444 0.000039 0.000483 ( 0.000482) all?-item 0.000325 0.000078 0.000403 ( 0.000402) opt-method 0.655959 0.033814 0.689773 ( 0.708515) opt-item 0.000316 0.000001 0.000317 ( 0.000317) ---------------------------------------- Benchmark case: tail0 user system total real all?-method-1 9.412810 0.231126 9.643936 ( 9.681118) all?-method-2 5.375075 0.137908 5.512983 ( 5.754550) all?-method-3 5.226132 0.167640 5.393772 ( 5.507031) all?-item 0.873700 0.007545 0.881245 ( 0.917210) opt-method 5.319648 0.172547 5.492195 ( 5.633140) opt-item 0.174349 0.001974 0.176323 ( 0.183002) ---------------------------------------- Benchmark case: head0 user system total real all?-method-1 0.002421 0.000068 0.002489 ( 0.002489) all?-method-2 0.002169 0.000213 0.002382 ( 0.002382) all?-method-3 0.001624 0.000026 0.001650 ( 0.001651) all?-item 0.000623 0.000001 0.000624 ( 0.000624) opt-method 4.779120 0.146312 4.925432 ( 4.951167) opt-item 0.000629 0.000001 0.000630 ( 0.000629) ---------------------------------------- Benchmark case: all1 user system total real all?-method-1 9.379650 0.255865 9.635515 ( 9.683078) all?-method-2 4.950280 0.150659 5.100939 ( 5.140174) all?-method-3 4.857898 0.129125 4.987023 ( 5.003142) all?-item 0.694113 0.001295 0.695408 ( 0.702370) opt-method 5.032373 0.121708 5.154081 ( 5.189599) opt-item 0.170540 0.002069 0.172609 ( 0.180343) ```