declarative_evil.pl

  # All the primes...
    constant p = [  (1..∞).grep(&is-prime)  ];

    # The definitions of "strong" and "weak"...
    sub strong (\n)  { n > 0 && p[n] > p[n-1, n+1].sum/2 }
    sub weak   (\n)  { n > 0 && p[n] < p[n-1, n+1].sum/2 }

    # All the strong and weak primes...
    constant strong-p = p.kv.map: ->\n,\pₙ {pₙ if strong n};
    constant   weak-p = p.kv.map: ->\n,\pₙ {pₙ if   weak n};

    # Print out the first ten...
    say 'strong primes: ', strong-p[^10];
    say 'weak primes:   ',   weak-p[^10];