Find prime n such that reversed n is also prime: Difference between revisions

=={{header|OCaml}}==

Using the function <code>seq_primes</code> from [[Extensible prime generator#OCaml]]:

<syntaxhighlight lang="ocaml">let int_reverse =

let rec loop m n =

if n < 10 then m + n else loop ((m + n mod 10) * 10) (n / 10)

in loop 0

let is_prime n =

let not_divisible x = n mod x <> 0 in

seq_primes |> Seq.take_while (fun x -> x * x <= n) |> Seq.for_all not_divisible

let () =

seq_primes |> Seq.filter (fun p -> is_prime (int_reverse p))

|> Seq.take_while ((>) 500) |> Seq.iter (Printf.printf " %u") |> print_newline</syntaxhighlight>

{{out}}

<pre> 2 3 5 7 11 13 17 31 37 71 73 79 97 101 107 113 131 149 151 157 167 179 181 191 199 311 313 337 347 353 359 373 383 389</pre>