[ruby-core:117155] [Ruby master Feature#4247] New features for Array#sample, Array#choice

Issue #4247 has been updated by mame (Yusuke Endoh).

Status changed from Assigned to Rejected
Assignee deleted (mame (Yusuke Endoh))

We discussed this at the dev meeting. No one remembered the discussion from over 10 years ago, so we discussed it anew and concluded that this was a no-go.

A naive API design could be `ary.sample(k, weights: [Float])`, but this would be an O(ary.size * k) time-consuming algorithm.

There are many more efficient algorithms for weighted sampling. (We read Julia's [StatsBase.jl](https://juliastats.org/StatsBase.jl/stable/sampling/) and Python's [random](https://docs.python.org/3.13/library/random.html).) However, these require additional information, such as the sum of the weights, cumulative weight table, the need to build the table in advance, etc.

We want to avoid an API design that only allows slow algorithm, but it seems overkill to introduce an API that allows advanced algorithms as a built-in feature. We concluded that it would be better to make a gem, instead of a built-in feature, for such things.



----------------------------------------
Feature #4247: New features for Array#sample, Array#choice
https://bugs.ruby-lang.org/issues/4247#change-107242

* Author: oj (Yoji Ojima)
* Status: Rejected
----------------------------------------
=begin
 We are planning to add the following features of the random sampling to Array.
 
 1. Weighted random sampling.
 2. Sampling with replacement.
 3. Iteration.
 
 It is discussed in ruby-dev (Feature #3647 and #4147).
 
 
 API will be:
 
 Array#sample([size, [opt]])
   - Random selection without replacement.
   - Returns a new array when size is specified.
   - opt:
       weight: proc or array
       random: Random instance
 
 Array#choice([size, [opt]])
   - Random selection with replacement.
   - Returns a new array when size is specified.
   - opt: same as above.
 
 Array#each_sample([opt])
   - Random selection iterator without replacement.
   - Choose a random element and yield it.
   - Returns an Enumerator if a block is not given.
   - opt: same as above.
 
 Array#each_choice([opt])
   - Random selection iterator with replacement.
   - Choose a random element and yield it.
   - Returns an Enumerator if a block is not given.
   - opt: same as above.
 
 
 Comments?
=end




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