Add a method to overwrite a bitset.

[plietar]

This copies the value from one bitset to another one.

[giovannic]

Functionally this is fine.

I'm guessing this is to avoid memory allocation in $copy? If so, we could we make those implications clear in the docs for $copy and $assign

[plietar]

Somehow it hadn't even crossed my mind to just use copy for this. This does have a slight difference in behaviour in the case where the bitset is aliased, not that it matters much for the usecase I want it:

This will modify both x and y (since they are the same bitset):

x <- Bitset$new(10)
y <- x
x$assign(z)

Where as this will only modify x, by creating a new bitset:

x <- Bitset$new(10)
y <- x
x <- z$copy()

I still think this is useful to have. I'm not sure I love the name though. An alternative could be copy_from, inspired by Rust's clone_from.

I'll add the extra note to the docs you suggested.

[plietar]

I've changed my mind and renamed to copy_from. Let me know what you think.