Palindromic primes in base 16: Difference between revisions

 

=={{header|REXX}}==

parse arg hi cols . /*obtain optional argument from the CL.*/

if cols=='' | cols=="," then cols= 10 /* " " " " " " */

call genP /*build array of semaphores for primes.*/

w= 8 /*max width of a number in any column. */

finds= 0; idx= 1 /*define # of palindromic primes & idx.*/

$= /*hex palindromic primes list (so far).*/

x= d2x(j); if x\==reverse(x) then iterate /*Hex value not palindromic? " " */

finds= finds + 1 /*bump the number of palindromic primes*/

lowerHex: return translate( arg(1), 'abcdef', "ABCDEF") /*convert hex chars──►lowercase.*/

/*──────────────────────────────────────────────────────────────────────────────────────*/

@.1=2; @.2=3; @.3=5; @.4=7; @.5=11 /*define some low primes. */

!.2=1; !.3=1; !.5=1; !.7=1; !.11=1 /* " " " " flags. */

#=5; s.#= @.# **2 /*number of primes so far; prime². */

/* [↓] generate more primes ≤ high.*/

parse var j '' -1 _; if _==5 then iterate /*J divisible by 5? (right dig)*/

if j// 3==0 then iterate /*" " " 3? */

{{out|output|text=  when using the default inputs:}}

<pre>

───────┼───────────────────────────────────────────────────────────────────────────────────────────

1 │ 2 3 5 7 b d 11 101 151 161

11 │ 191 1b1 1c1

───────┴───────────────────────────────────────────────────────────────────────────────────────────

</pre>