Descending primes: Difference between revisions

=={{header|Ruby}}==

<lang ruby>require 'prime'

digits = [9,8,7,6,5,4,3,2,1]

res = 1.upto(digits.size).flat_map do |n|

digits.combination(n).filter_map do |set|

candidate = set.join.to_i

candidate if candidate.prime?

end.reverse

end

puts res.join(",")</lang>

{{out}}

<pre>2,3,5,7,13,17,19,23,29,37,47,59,67,79,89,127,137,139,149,157,167,179,239,257,269,347,349,359,367,379,389,457,467,479,569,1237,1249,1259,1279,1289,1367,1459,1489,1567,1579,1789,2347,2357,2389,2459,2467,2579,2689,2789,3457,3467,3469,4567,4679,4789,5689,12347,12379,12457,12479,12569,12589,12689,13457,13469,13567,13679,13789,15679,23459,23567,23689,23789,25679,34589,34679,123457,123479,124567,124679,125789,134789,145679,234589,235679,235789,245789,345679,345689,1234789,1235789,1245689,1456789,12356789,23456789

</pre>