Ruby has a terrific implementation of single-valued permutations, but it
doesn’t yield the results I expected when using arrays of arrays. For
example:
[[1, 2], [2, 3]].permutation.to_a.include? [2, 1]
=> false
The reason is that there’s no permutation of the sub-arrays, just of the
top-level array elements. Am I overlooking something obvious here? I’d
like the permutations to include randomization within each sub-array,
too.