with javascript_semantics
include mpfr.e
function mpz_srb(string input, integer n)
    mpz res = mpz_init("0b"&input),
        tmp = mpz_init_set(res),
        bit = mpz_init(1),
       mask = mpz_init(power(2,n+1)-1),
       rask = mpz_init() -- (mask res)
    for i=1 to length(input) do -- (backward, actually)
        if mpz_even(tmp) then
            mpz_and(rask,tmp,mask)
            if mpz_cmp_si(rask,0)!=0 then
                mpz_add(res,res,bit)
            end if
        end if
        mpz_mul_2exp(bit, bit, 1)    -- aka left shift
        mpz_fdiv_q_2exp(tmp, tmp, 1) -- aka right shift
    end for
    string ret = mpz_get_str(res,2)
    integer lz = length(input)-length(ret)
    if lz then ret = repeat('0',lz)&ret end if
    return ret
end function
--...
        printf(1,"n = %d: %s\n",{n,mpz_srb(input,n)})