From: muraken@... Date: 2020-06-18T02:06:17+00:00 Subject: [ruby-core:98846] [Ruby master Feature#16812] Allow slicing arrays with ArithmeticSequence Issue #16812 has been updated by mrkn (Kenta Murata). It may be better to change the behavior of `[*0..10][-100..100]` because `[*0..10][..100]` does not return `nil`: ``` [*0..10][..100] # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] ``` And the following cases seems inconsistent to me: ``` [*0..10][0..12] # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] [*0..10][-12..-1] # => nil ``` ---------------------------------------- Feature #16812: Allow slicing arrays with ArithmeticSequence https://bugs.ruby-lang.org/issues/16812#change-86209 * Author: zverok (Victor Shepelev) * Status: Assigned * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) ---------------------------------------- I believe when concepts of ArithmeticSequence and `Range#%` were introduced, one of the main intended usages was array slicing in scientific data processing. So, it seems to make sense to allow this in `Array#[]`: ```ruby ary[(5..20) % 2] # each second element between 5 and 20 ary[(0..) % 3] # each third element ary[10.step(by: -1)] # elements 10, 9, 8, 7 .... ``` PR is [here](https://github.com/ruby/ruby/pull/3055). My reasoning is as follows: 1. As stated above, ArithmeticSequence and `Range#%` seem to have been introduced exactly for this goal 2. Python has its slicing syntax as `begin:end:step` (with a possibility to omit either), and it seems to be well respected and used feature for data processing. So I believe it is useful, and relatively easy to integrate into existing functionality I expect the usual "it is ugly and unreadable!" backlash. I don't have an incentive, nor energy, to "defend" the proposal, so I would not. -- https://bugs.ruby-lang.org/ Unsubscribe: