Re: Best way to get ceil(log2(x)) of a BigInt?

[pineapple via Digitalmars-d-learn]

On Wednesday, 2 November 2016 at 14:24:42 UTC, Andrea Fontana 
wrote:
On Wednesday, 2 November 2016 at 14:05:50 UTC, pineapple wrote:
I'm trying to do some math stuff with std.bigint and realized 
there's no obvious way to calculate the ceil of log2 of a 
bigint. Help?

How big are your bigints?

I think they'll generally stay between 0 and 2^200

I came up with this, I guess it'll work?

   auto clog2(BigInt number) in{
        assert(number > 0);
    }body{
        uint log;
        auto n = number - 1;
        while(n > 0){
            log++; n >>= 1;
        }
        return log;
    }