Mixed int/BigInt foreach interval

[bearophile]

Timon Gehr:

> I mean, eg. the following is hardly useful:
> 
> foreach(i;0..BigInt("10000000000000000000000000"){}

I'd like a function template like this to work even if T is BigInt:

T binomial(T)(T n, T k) {
    if (k > n/2)
        k = n - k;
    T bc = n - k + 1;
    foreach (i; 2 .. k+1)
        bc = (bc * (n - k + i)) / i;
    return bc;
}


Current workaround: use this instead of the foreach:
for (T i = 2; i <= k; i++)

----------------------------

Christophe:

> The copy on write behavior of BigInt makes it very poorly efficient
> to iterate on. In addition, I guess the compiler won't be able to
> optimize anything. Someone could say this is a good reason to make the
> .. syntax on BigInt harder to use.

I'd like to use BigInts often in D. So some compiler optimizations are welcome here.

Bye,
bearophile