util: add GrayCode

[ekiwi]

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you state the API impact?
• Did you specify the code generation impact?
• Did you request a desired merge strategy?

Type of Improvement

• new feature/API

API Impact

• adds two new utility functions to convert binary to gray code and back

Backend Code Generation Impact

• this change does not impact existing code

Desired Merge Strategy

• squash

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels?
• Did you mark the proper milestone (Bug fix: 3.4.x, [small] API extension: 3.5.x, API modification or big change: 3.6.0)?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you mark as Please Merge?

[aswaterman]

This is a good util to have.

I'm pretty sure that the GrayToBinary is just something like

Cat((in.getWidth - 2 to 0 by -1).scanLeft(in.head(1)) { case (prev, ii) => prev ^ in(ii) }

so you can get rid of the var.

[aswaterman]

lgtm

[ekiwi]

@jackkoenig Did you want to backport this?

[jackkoenig]

@jackkoenig Did you want to backport this?

Why not!