enum RID, I, SAMPLE

function s_of_n(sequence env, integer item)
    integer i = env[I] + 1,
            n = length(env[SAMPLE])
    env[I] = i
    if i<=n then
        env[SAMPLE][i] = item
    elsif n/i>rnd() then
        env[SAMPLE][rand(n)] = item
    end if
    return env
end function

function s_of_n_creator(int n)
    return {routine_id("s_of_n"),0,repeat(0,n)}
end function

function invoke(sequence env, args)
    env = call_func(env[RID],prepend(args,env))
    return env
end function

function test(integer n, sequence items)
    sequence env = s_of_n_creator(n)
    for i=1 to length(items) do
--      env = s_of_n(env,items[i])
        env = invoke(env, {items[i]})
    end for
    return env[SAMPLE]
end function

procedure main()
    sequence items_set = tagset(9,0)
    sequence frequencies = repeat(0,length(items_set))
    for i=1 to 100000 do
        sequence res = test(3, items_set)
        for j=1 to length(res) do
            frequencies[res[j]+1] += 1
        end for
    end for
    ?frequencies
end procedure
main()