Checking for exactly one signal out of four wires?

[peak summit]

What solutions have you come up with? I struggled with this today and wonder what kind of simpler solutions might there be.

I'm working on a stacker that can handle 1-4 quarters. I have four wires for shape quarters. If exactly one quarter is null, I direct the three remaining quarters to another stacker complex than if there were four, and so on.

I ended up testing each wire separately against all the other three (with xor gates) and then combining the conclusion and fried my brain. The design works but takes up space.

[ripe olive]

I would split it into simpler steps:
||1 - if (A&&B) then stack A with B to make E, else output A/B as E without stacking
2 - if (C&&D) then stack C with D to make F, else output C/D as F without stacking
3 - if (E&&F) then stack E and F to make output, else output E/F without stacking||

[stark gull]

yep, ||stacking each quadrant and then each halves with a bypass at each step|| is the most common way of handling this problem

[dense glen]

Need 3 stackers to stack 4 shapes. Easiest way is to think of each stacker independently. If both inputs are present then stack them, otherwise bypass (send the input directly to the output).

[peak summit]

I redid my auto-stacker today, still had to put a lot of gates to account for all possible scenarios where and how many missing quadrants there are, but at least it works. Also it takes a lot of space but I can clean it up later. Thanks for the tips 😊😊

[ripe olive]

if you want to take a look at how I implemented similar logic, I just uploaded my smart swapper today - it relies on the same logic as a smart stacker would
https://discord.com/channels/1000343719314198548/1410661419183112192

[stark gull]

it's pretty much just if both inputs are here, don't bypass, otherwise bypass

[peak summit]

Thanks, that looks so much more complex than my brain can handle yet 😁 Small steps...

[ripe olive]

here is a simplified form of the logic in it - maybe it will be more understandable when it is not all tangled up XD