In this example, you could have just made a constant with value 0 and returned a reference to that. It would also have a 'static lifetime and there would be no leaking.
I believe the intention was to demonstrate something that works with runtime values too, and a constant 0 does not.
Btw you can just write &0 to do what you proposed, there’s no need for an explicit constant/static.
I can agree that the example function is not the best usecase. But the point still stand that there’s no realistic escape hatch from lifetimes and memory management in Rust.
Cow does not work when you are actually required to return a reference, e.g. if you’re working with some other crate that requires that. Cow also has some more strict requirements on reborrows (i.e. you can reborrow a &'short &'long T to a &'long T, but you can only reborrow a &'short Cow<'long, T> to a &'short T).
LazyLock can solve very specific issues like static, but is not a general escape hatch. Again, the example is not the best to showcase this, but imagine if you have to perform this operation for an unknown amount of runtime values. LazyLock will only work for the very first one.
but imagine if you have to perform this operation for an unknown amount of runtime values
This is a poor argument. You dont write code like this in rust. If you can find a situation where it is an actual issue we can discuss things but to just say imagine this is a problem when it very likely is not a problem that can be solved in a better way at all let alone a common one is a very poor argument.
Typically when you want an escape from lifetimes that means you want shared ownership of data which you can do with an Arc. Cow and LazyLock can also help in situations - but to dismiss all these for some imagined problem is a waste of time. Comes up with a concrete example where it would help. Very likely you would find another way to solve the problem in any realistic situation you can come up with that I would suspect leads to a better overall design for a rust program.
I would say this is just a straw man argument - but you have not even created a straw man to begin with, just assume that one exists.
I perfectly agree, that would be horrible code! I would generally try to restructure my code, making it better fit the actual lifetimes of the data I’m working with. The point in the article is that you can’t really escape from this. I’m not arguing this is a real problem, and I don’t think the article is neither, just pointing out that this is something you can easily do in C# and not in Rust. It’s just a difference between the two languages.
What? You can easily escape from it if there are better alternatives you can use. Pointing at one language and saying it is not easy to code like it is another language is a pointless argument. You can do that about any two languages. They all differ for good reasons and as long as you can solve similar problems in both, even if in different ways then what does it matter that you cannot do it in the same way?
What? You can easily escape from it if there are better alternatives you can use.
So there is no general escape hatch.
Pointing at one language and saying it is not easy to code like it is another language is a pointless argument.
I’m not arguing that it is easier to code in C# than in Rust, just that this particular escape hatch is possible in C# and not in Rust. It’s just an observation.
They all differ for good reasons and as long as you can solve similar problems in both, even if in different ways then what does it matter that you cannot do it in the same way?
(Note that I’m not the article author)
I believe the intention was to demonstrate something that works with runtime values too, and a constant 0 does not.
Btw you can just write
&0to do what you proposed, there’s no need for an explicit constant/static.Optionnot an option?Cows?LazyLockstatic?I can agree that the example function is not the best usecase. But the point still stand that there’s no realistic escape hatch from lifetimes and memory management in Rust.
Cowdoes not work when you are actually required to return a reference, e.g. if you’re working with some other crate that requires that.Cowalso has some more strict requirements on reborrows (i.e. you can reborrow a&'short &'long Tto a&'long T, but you can only reborrow a&'short Cow<'long, T>to a&'short T).LazyLockcan solve very specific issues likestatic, but is not a general escape hatch. Again, the example is not the best to showcase this, but imagine if you have to perform this operation for an unknown amount of runtime values.LazyLockwill only work for the very first one.This is a poor argument. You dont write code like this in rust. If you can find a situation where it is an actual issue we can discuss things but to just say imagine this is a problem when it very likely is not a problem that can be solved in a better way at all let alone a common one is a very poor argument.
Typically when you want an escape from lifetimes that means you want shared ownership of data which you can do with an Arc. Cow and LazyLock can also help in situations - but to dismiss all these for some imagined problem is a waste of time. Comes up with a concrete example where it would help. Very likely you would find another way to solve the problem in any realistic situation you can come up with that I would suspect leads to a better overall design for a rust program.
I would say this is just a straw man argument - but you have not even created a straw man to begin with, just assume that one exists.
I perfectly agree, that would be horrible code! I would generally try to restructure my code, making it better fit the actual lifetimes of the data I’m working with. The point in the article is that you can’t really escape from this. I’m not arguing this is a real problem, and I don’t think the article is neither, just pointing out that this is something you can easily do in C# and not in Rust. It’s just a difference between the two languages.
What? You can easily escape from it if there are better alternatives you can use. Pointing at one language and saying it is not easy to code like it is another language is a pointless argument. You can do that about any two languages. They all differ for good reasons and as long as you can solve similar problems in both, even if in different ways then what does it matter that you cannot do it in the same way?
So there is no general escape hatch.
I’m not arguing that it is easier to code in C# than in Rust, just that this particular escape hatch is possible in C# and not in Rust. It’s just an observation.
It does not really matter, but does it have to?