SALSA Implementation

[TDebono]

Hey there!

I have a general question regarding the SALSA implementation you are using here (see screenshot below). I'm struggling to fully comprehend why the part that I highlighted yields the desired output. I've tried mapping this implementation to "textbook descriptions" (e.g., Lempel & Moran 2001) of the algorithm but feel like I'm missing something here.

Would be highly appreciated if you could provide some intuition as to how/why the highlighted part yields the desired output.

Thanks!

Best,
Timo