Rust in 2018: easier to use

Re:Rust in 2018: easier to use by red75prime on Sunday January 14, 2018 @02:46AM (#16143251)

Read the books, write code. When you'll encounter lifetimes, it's good to remember that lifetime annotations are descriptive and not prescriptive. You can't change lifetime of a variable by adding lifetime annotations.

For example, local variables of a function get destroyed on function exit no matter what and you can't prevent it by adding lifetime annotation to a local variable reference you are trying to return.

That was a stumbling block for me.

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Re:Rust in 2018: easier to use by littlestymaar on Sunday January 14, 2018 @07:41AM (#16144025)

You summarized it so well ! It was also a huge source of confusion for me in the beginning.

Would you mind if I made a pull request to the Rust book adding your explaination to the lifetime chapter ?

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Re:Rust in 2018: easier to use by steveklabnik on Sunday January 14, 2018 @02:54PM (#16145980)

While it doesn't have this literal text, it already does have the equivalent: https://doc.rust-lang.org/book/second-edition/ch10-03-lifeti...

> Lifetime annotations don’t change how long any of the references involved live. In the same way that functions can accept any type when the signature specifies a generic type parameter, functions can accept references with any lifetime when the signature specifies a generic lifetime parameter. What lifetime annotations do is relate the lifetimes of multiple references to each other.

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Re:Rust in 2018: easier to use by littlestymaar on Monday January 15, 2018 @03:48AM (#16149361)

Cool. I haven't read the second version of the book, and I read the first version about two years ago I think. Glad to see this difficulty is now covered. Carry on with the great job Steve :)

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Re:Rust in 2018: easier to use by steveklabnik on Monday January 15, 2018 @08:26AM (#16150309)

Ah ha! Yeah, it's quite different.

Thanks :)

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Re:Rust in 2018: easier to use by red75prime on Sunday January 14, 2018 @08:05AM (#16144094)

I wouldn't. Feel free to use it. But I have the impression that the Rust book contains something to that effect.

"Descriptive and not prescriptive" part probably comes from stackoverflow. I don't remember exactly.

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Re:Rust in 2018: easier to use by steveklabnik on Sunday January 14, 2018 @02:53PM (#16145977)

I'm not sure where I heard it, but I certainly repeat it. It's not literally in the book though, I'll also reply to your parent about this.

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