Paste: another nsieve

: init-sieve ( n -- xs )
    [ 1 ] B{ } replicate-as
    0 over set-first
    0 over set-second ; inline

: set-all ( elt indices seq -- )
    swap [ swap set-nth ] with with each ; inline

: multiples ( i n -- range )
    over [ 2 * ] [ 1 - ] [ ] tri* <range> ;

:: nsieve ( n -- pi(n) )
    [let | xs [ n init-sieve ] |
        xs [| i |
            1 = [
                0 i n multiples xs set-all
            ] when
        ] each-index 
        xs sum
    ] ;