Rare numbers: Difference between revisions

 

=={{header|F_Sharp|F#}}==

This solution demonstrates the concept described in [[Talk:Rare_numbers#30_mins_not_30_years]]. It uses [[Cartesian_product_of_two_or_more_lists#Extra_Credit]]

<lang fsharp>

l|>Seq.map(fun n->Seq.fold(fun(n,g) (n',g')->(n+n',g+g'))(0L,0L) n)|>Seq.filter(fun(n,g)->g>(pown 10L (a-1)) && izPS(n+g))

</lang>

<lang fsharp>

[2..12]|>Seq.collect rN |> Seq.iter(printfn "%A")

Real: 00:00:58.835, CPU: 00:01:00.421, GC gen0: 3220, gen1: 441, gen2: 16

</pre>

=={{header|Go}}==

As in the case of the REXX entry, this takes into account all the hints within Shyam Sunder Gupta's webpage. It also makes use of his observation that no rare number below 10^20 ends in 3 and uses a bit arithmetic trick to further filter out numbers that cannot be perfect squares and thereby avoid the expensive math.Sqrt operation.