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by braythwayt 2259 days ago
Not only is the answer "Yes, a Turing machine can be constructed out of GoL, demonstrating that GoF is universal," but given that GoL is itself a computation, the reverse is true: You can build GoL out of a Turing machine.

I took a stab at it a few years ago. My strategy was to start with a very basic Turing Machine, and then write a compiler that compiled a more sophisticated Turing Machine out of a simpler Turing Machine.

For example, when I wanted cells to have a value and a tag, I wrote a compiler that translated every possible combination of symbol and tag into a single flat space of symbols.

I stacked compiler on top of compiler until I had a Langdon's Ant with various programming conveniences, and I wrote a 9-cell GoL using my Langdon's Ant.

The whole thing compiled to a very simple TM with millions of states, but it worked. I did not make it practical enough to ever manage a GoL big enough to emulate a Turing machine, but I feel that I did enough to get some practical experience with something that is straightforward in theory.

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Turing Machine in GoL: https://www.youtube.com/watch?v=My8AsV7bA94