[crdrost]

“Have you tried turning off and on again?” is advice to perform a total state reset, which works because the system’s state is inconsistent but its sources of truth are not.

You never have to reset state if you do not have it in the first place. You get other bugs still, but you don't have the most common class of bugs.

But, you need some state. You just want to discourage it. Some of it can come from laziness, but with difficulty. (Chris Okasaki’s Purely Functional Data Structures uses it to de-amortize the bound on a FIFO queue.) Other things, like ring buffers, are harder to argue.

So you want to be able to express an array of IORefs, say, for your ring buffer. But the people who use it become aware that it is a stateful construct and must be used that way.

Read “what color is your function?” for a counterpoint, of course.