;;; find some additive primes - primes whose digit sum is also prime
;;; Library: Action! Sieve of Eratosthenes
INCLUDE "H6:SIEVE.ACT"

PROC Main()
  DEFINE MAX_PRIME = "500"

  BYTE ARRAY primes(MAX_PRIME)
  CARD n, digitSum, v, count

  Sieve(primes,MAX_PRIME)

  count = 0
  FOR n = 1 TO MAX_PRIME - 1 DO
    IF primes( n ) THEN
      digitSum = 0
      v = n
      WHILE v > 0 DO
        digitSum ==+ v MOD 10
        v ==/ 10
      OD
      IF primes( digitSum ) THEN
        IF n < 100 THEN
          Put(' )
          IF n < 10 THEN Put(' ) FI
        FI
        Put(' )PrintI( n )
        count ==+ 1
        IF count MOD 20 = 0 THEN PutE() FI
      FI
    FI
  OD
  PutE()Print( "Found " )PrintI( count )Print( " additive primes below " )PrintI( MAX_PRIME + 1 )PutE()
RETURN