CA UTM without guns?

[Koiti Kimura]

How can you give a CA the three kinds of logic gates without guns? Would anyone explain the principles outlines to me, a CA-ology beginner?

[BlinkerSpawn]

How can you give a CA the three kinds of logic gates without guns? Would anyone explain the principles outlines to me, a CA-ology beginner?

Well, you can't, really.
The AND and OR are fine: Just let two signals collide to create a new signal, and in the case of OR, delete singleton signals.
A NOT gate is impossible without guns, however. To illustrate this, imagine I set upa NOT gate and then never gave it a signal. It would produce a signal every N generations (N being the time distance between consecutive cycles, or the "clock speed"), which is exactly what a gun does.
However, logical universality only requires the use of an ANDNOT gate (also called a Fredkin gate IIRC) which would look a lot like this:

Code: Select all

x = 14, y = 28, rule = 345/2/3
12.A$11.3A$12.A4$BA5.BA$BA5.BA5$12.2A$12.2B13$12.2A$12.2B!

A signal is output only if one signal is present ANDNOT the other.
Besides that, all that would remain would be simple wiring (turns, splitters, delays, etc.)

[Macbi]

You could use some other signal instead of gliders, such as Hershels.

[BlinkerSpawn]

You could use some other signal instead of gliders, such as Hershels.

Hence why I used the general term "signals" in my explanation, which could be spaceships or hassleable methuselae.
Generally, spaceships make much better signals due to the existence of more degrees of freedom in space and time.