Issue #21564 has been reported by toy (Ivan Kuchin). ---------------------------------------- Feature #21564: Extend permutation, repeated_permutation, combination and repeated_combination argument https://bugs.ruby-lang.org/issues/21564 * Author: toy (Ivan Kuchin) * Status: Open ---------------------------------------- When using functions `permutation`, `repeated_permutation`, `combination` and `repeated_combination`, often one needs not one, but multiple permutation/combination sizes. Currently all functions accept one Integer argument (for `permutation` it is optional and defaults to array size), and it would be more powerful if it would accept also a range or a Enumerable: ```ruby a = [1, 2, 3] a.permutation(1..3).to_a # => [[1], [2], [3], # [1, 2], [1, 3], [2, 1], [2, 3], [3, 1], [3, 2], # [1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]] a.permutation([1, 3]).to_a # => [[1], [2], [3], # [1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]] a.permutation([3, 1]).to_a # => [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1], # [1], [2], [3]] a.repeated_permutation([2, 1]).to_a # => [[1, 1], [1, 2], [1, 3], [2, 1], [2, 2], [2, 3], [3, 1], [3, 2], [3, 3], # [1], [2], [3]] a.combination(1..3).to_a # => [[1], [2], [3], # [1, 2], [1, 3], [2, 3], # [1, 2, 3]] a.repeated_combination(1..3).to_a # => [[1], [2], [3], # [1, 1], [1, 2], [1, 3], [2, 2], [2, 3], [3, 3], # [1, 1, 1], [1, 1, 2], [1, 1, 3], [1, 2, 2], [1, 2, 3], [1, 3, 3], [2, 2, 2], [2, 2, 3], [2, 3, 3], [3, 3, 3]] ``` Ruby code to enhance current `permutation` would be: ```ruby class Array alias_method :original_permutation, :permutation def permutation(counts, &block) return to_enum(__method__, counts) unless block if counts.is_a?(Enumerable) counts.each do |count| original_permutation(count, &block) end else original_permutation(counts, &block) end end end ``` -- https://bugs.ruby-lang.org/