SlySherZ

Do you know how to create a local branch that tracks a gerrit commit? Usually I just do git commit --amend to update gerrit, but then I lose access to my patch's history (it's still on gerrit, but I want it locally).

The article is hard to follow for me, but if I understood it correctly, this is not true:

> That is just not going to happen in (classical) reality, though. Because once you properly set the initial state of the ball (force=velocity=0, or any other values), then the solution becomes unique

If you set velocity = velocity = 0, then the ball staying at the top is a valid solution, AND the ball rolling down the hill (in any direction) is also a valid solution.

If this sounds confusing (it did for me), look at the example at the end, it's possible to do the reverse - send the ball rolling up the hill with perfect velocity, such that it stops at the very top after time T. And if that is possible, the opposite is also possible because NM is time reversible.

There's a common way people from scientific communities (such as HN) look at the world - there's a "real world" out there, and in order to improve our understanding of things we should approximate (discover the rules that govern) this real world and try to minimize our subjective experiences as much as possible. I fully subscribe to this view, the real world has to be same for everyone, right?

But there's another way to look at things which is prevalent in other circles, and if someday you decide to learn to meditate, I'm confident you'll get it.

How do you know the "real world" exists? Maybe you're a brain inside a jar "in the machine", and all the things you experience are being generated by the machine. In that case, how is an hallucination any different from any other experience you have? It isn't, it's exactly the same, it's just another experience. How you interpret it may be different, if you realize it's an hallucination, but the process itself is the same.

When you look at a tree, you can't just see the tree, you can only see the model that your mind creates of that tree, from the light that reaches your eyes, the sound, maybe touch etc - this is true for everything you experience.

Obviously the first perspective is very useful, it's science. But the second perspective is also very very useful, if you want to know why I can elaborate : )

Portugal, either Porto or Braga. Let me know if you'd like to meet!

Alright, I'll try.

Last time you used an higher level interpreted language (like JS), did you have to worry whether or not the machine instructions it was generating were the right ones? Generating instructions at runtime sounds pretty unsafe, no?

You didn't, right? You can just mostly assume the language works and get on with your life. That's how unsafe feels to me when I'm programming in Rust, I never have to worry about it and pretty much never need to use it.

Sometimes you'll run into a problem where you need to use unsafe, but that only happens very very rarely, for example when creating an interface to a C library, but most people will never need that. When that happens, sure, you'll have to be extra careful and make sure everything works. But after you're done with that small piece, you're back into safe Rust.

So, how does it work in practice, if you really need to use unsafe? Suppose you have a C enum with values MyEnum {A, B, C} (but it can be any int in C!), and you want to use it in Rust. You can make an unsafe wrapper that tries to parse the enum, and it can either return None - if it was an invalid integer, or return Some(A), Some(B), Some(C).

But once you get the wrapper right (which is not hard), Rust will guarantee that values of type MyEnum have values A, B or C and nothing else, so you never need to worry about the exceptional case again.

You worry about it once at the boundary and that's it.