some_primes.dc

# let's print some primes:
# we have some helper functions, the main work is done by 'is-prime?' below.
# Then the primes are printed by a loop-through, and the '.rj' format
# directive is used to keep them right-aligned.

: is-2-3-5-7?
    dup dup         # n n n
    2 =             # n n bool
    swap dup        # n bool n n
    3 =             # n bool n bool
    swap dup        # n bool bool n n
    5 =             # n bool bool n bool
    swap            # n bool bool bool n
    7 =             # n bool bool bool bool
    or or or        # n bool
;

: check-higher-than-49
  dup                             # n n
  sqrt ceil 1 +  6 /              # n n
  ceil 6 * 12 6 for
    dup i 1 - % 0 =
    over i 1 + % 0 =
    or if
      drop 0 exitfor
    else
      next drop 1
    endif
;

: is-not-div-otherwise?
  dup                         # n n
  49 < if                     # n bool
    drop 1
  else
    check-higher-than-49
  endif
;

: is-not-div-by-2-3-5-7?
    dup             # n n
    2 % 0 =         # n bool
    over            # n bool n
    3 % 0 =         # n bool bool
    or over         # n bool n
    5 % 0 =         # n bool bool
    or over         # n bool n
    7 % 0 =         # n bool bool
    or
    if
      drop 0
    else
      is-not-div-otherwise?
    endif
;

: is-prime
    is-2-3-5-7?
    if
      drop 1
    else
      is-not-div-by-2-3-5-7?
    endif
;

: test-primes
  8192 2 1 for
    i is-prime
    if
      i 4 0 .rj
    else
    endif
  next
  cr
;

" \n                           #### Some primes! ####\n \b" print
test-primes