rubyenumerable

Ruby: how to split a collection (Enumerable) in multiple (>2) partitions by some predicate?

Is there a function, to partition a collection (Enumerable) by some non-boolean predicate into more than 2 partitions? (my math knowledge got rusty - but I think, this was called "factorize" - or at least in German "Faktorisierung")
This follows my own yesterday question (Ruby: how to split a collection by predicate into two collections in ruby?)
and I wonder, is there another standard ruby method I just missed.

Here´s an example, showing the principle:

def factorize(eee)
  h={}; h.default_proc= proc{|h,k| h[k]=[] }
  eee.each{|e| k=yield e; h[k]<<e }
  h.values
end
factorize( 1..10 ){|n| n%3 }  #=> [[1, 4, 7, 10], [2, 5, 8], [3, 6, 9]]
Solution

  • You can use group_by: https://apidock.com/ruby/v2_5_5/Enumerable/group_by

    Example:

    (1..10).group_by { |n| n % 3 }.values
=> [[1, 4, 7, 10], [2, 5, 8], [3, 6, 9]]