CSS: Turing complete?

Posted in Bad Ideas, Programming - August 15, 2012 - 0 Comment

“The simple selector matches if all of its components match. ” according to the W3.org page on selectors. That sounds to me like an AND gate, in that something is selected if the logical AND of its components match.

Combine that with logical inversion, provided by the not selector, and it seems to me that you get NAND, which is a universal gate. Any boolean function can be composed of NAND gates, so it is in theory possible to compose an entire CPU out of NAND gates.

This makes it seem to me like you could write a processor simulation in CSS.

The main thing that I wonder about is how browsers evaluate CSS, because if it is not re-evaluated until nothing happens (e.g. nothing gets its attributes changed) then the CPU wouldn’t work because the “output” of a selection would not be able to be used as input into more selections (e.g. by changing their classes). Heck, I’m not sure you can even have CSS change the classes of an element on the fly.

But if you can…