minus :=
  \xs ys .
  [ x := car xs; y := car ys; xs' := cdr xs; ys' := cdr ys
  . lt? x y
        (cons x (minus xs' ys))
        (gt? x y
             (minus xs ys')
             (minus xs' ys')) ];

union := foldr merge ();

merge :=
  [ merge' :=
    \xs ys .
    [ x := car xs; y := car ys; xs' := cdr xs; ys' := cdr ys
    . lt? x y
          (cons x (merge' xs' ys))
          (gt? x y
               (cons y (merge' xs ys'))
               (cons x (merge' xs' ys'))) ]
  . \xs ys .
    [ x := car xs; xs' := cdr xs . cons x (merge' xs' ys) ] ];

primes := (cons 2 (cons 3 (minus (enumFromThen 5 7) composites)));
composites := union (map (\n . map (%mul n) (enumFrom n)) primes);

main :=
  iomapM_ (\n . iobind_ (iowriteDec n) (%iowrite '\n')) (take 1000 primes);