Would like highest_{set|zero}_bit()

[seanyoung]

Using bitvec, I'm building a known bits optimization pass for my compiler. For this I need to know the highest set bit in a bitvec.

This can be implemented using u64::trailing_zeros(). Maybe it should be called: {leading|trailing}_{zeros|ones}().

[myrrlyn]

Thank you for this request!

I have created the methods {first,last}_{one,zero} which report the index of the first or last bit in the bit-slice set to the requested value, returning None on empty bit-slices.

I have also created the methods {leading,trailing}_{ones,zeros}, which report the length of the run of the requested bit at the corresponding end of the bit-slice, returning 0 on empty bit-slices.

Please let me know if these have the behavior you expect.

They will be included in the 0.21 released published before the end of the month.

[seanyoung]

@myrrlyn fantastic news, thank you very much!
They look exactly like what I need, let me test them and get back to you.
I will be using them here https://github.com/hyperledger-labs/solang/blob/main/src/codegen/strength_reduce.rs