swap using shift and log

[Heitor-Santos]

I just used a couple of shifts and log :)

[Prime-5]

Hey @Heitor-Santos
It's a good approach, but not foolproof. It worked for little numbers, but when I tried a=51 and b=32, it faulted.
So either document the error (if its related to the size of integer or something), or work a turnaround if possible.

I would like to add this method, thanks for the PR!