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Book: Be very explicit of lifetimes being descriptive #36997

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Oct 12, 2016
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Book: Be very explicit of lifetimes being descriptive #36997

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Book: Be very explicit of lifetimes being descriptive
KillTheMule Oct 6, 2016
7f02eb3
Distinguish lifetimes and their annotations
KillTheMule Oct 6, 2016
a542302
Another shot at clarity
KillTheMule Oct 6, 2016
2a0bd6d
Typos
KillTheMule Oct 6, 2016
0d0cdb7
Wrap & improve
KillTheMule Oct 7, 2016
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2 changes: 2 additions & 0 deletions src/doc/book/lifetimes.md
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Expand Up @@ -56,6 +56,8 @@ To fix this, we have to make sure that step four never happens after step
three. The ownership system in Rust does this through a concept called
lifetimes, which describe the scope that a reference is valid for.

**Note** It's important to understand that lifetime annotations are _descriptive_ not _prescriptive_. This means that the lifetimes of references are determined by the code, not by the annotations. The annotations, however, point out the lifetimes to the compiler in case it can't figure them out by itself.
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That's better, but I also think the phrase "the lifetimes of references" should also avoid the overloaded term "lifetime" (just as it says "the annotations" a bit later). This paragraph is clarifying a confusion between the two meanings of the word lifetime (one I've see a lot) so it should avoid anything which could be misinterpreted through the lens of that confusion. Perhaps something along the lines of "how long references are valid is determined by [...]".

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I gave it another shot, thanks for looking at it.


When we have a function that takes an argument by reference, we can be
implicit or explicit about the lifetime of the reference:

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