retroforth/example/Primes.forth

This is a quick and dirty way to find prime numbers in a set.

````
{{
  #2 'NextPrime var<n>
  :extract (s-s)
    [ @NextPrime dup-pair eq?
      [ drop-pair TRUE ]
      [ mod n:-zero? ] choose ] set:filter ;
---reveal---
  :get-primes (s-s)
    #2 !NextPrime
    dup fetch [ extract &NextPrime v:inc ] times ;
}}
````

And a test:

````
:create-set (-a)
  here #7000 , #2 #7002 [ dup , n:inc ] times drop ;

create-set get-primes [ putn sp ] set:for-each
````