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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 lifetimes are _descriptive_ not _prescriptive_. This means that the lifetimes of references are determined by the code, not by the lifetime 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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"the lifetimes of references are determined by the code, not by the lifetime annotations" is a bit ambiguous (because "lifetime" is super overloaded). Perhaps it would be better to spell out what the two occurrences of the word "lifetime" mean here:

  1. The time for which a reference is valid
  2. The 'a annotations

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I tried to make it clearer, making a distinction between "lifetime" and "lifetime annotation".


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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