Finding the nth LSB

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1

Is there some secret dark instruction to find the nth LSB without looping?
We call the secret instruction get() here.

For example for this 15 bit number:

const mask: u15 = 0b0101011110010001;

const a: u4 = get(mask, 0); // returns 0
const b: u4 = get(mask, 1); // returns 4
const c: u4 = get(mask, 2); // returns 7
const d: u4 = get(mask, 3); // returns 8
// etc.
2

These things can be done efficiently with the upcoming pext/pdep builtins, in your case @ctz(@depositBits(1 << pos, mynum)), where @ctz already exists in Zig and counts trailing zero (pdep alone would just leave the n’th bit set, with all other bits zeroed)

The PR is actively developed: Implement @depositBits and @extractBits by bnuuydev · Pull Request #23474 · ziglang/zig · GitHub

I believe for now you’ll have to write the lookup yourself

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3

I was already looking at pext stuff (which could be of use in other area’s of my program as well).
Thanks!! I’ll be back here tonight I think.

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