So far we’ve worked only with numbers, but Rust supports letters too. Rust’s char type is the language’s most primitive alphabetic type, and the following code shows one way to use it. (Note that char literals are specified with single quotes, as opposed to string literals, which use double quotes API documentation for the Rust `single_quote_char` macro in crate `prolog_parser` These are Rust's named lifetimes. Quoting from The Rust Programming Language: Every reference in Rust has a lifetime, which is the scope for which that reference is valid. Most of the time lifetimes are implicit and inferred, just like most of the time types are inferred
Data Types - The Rust Programming Language
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What is the significance of that apostrophe? Generic typing specific to references? I've no idea where the documentation for this is hiding. Quoting from The Rust Programming Language :. Every reference in Rust has a lifetime, which is the scope for which that reference is valid. Most of the time lifetimes are implicit and inferred, just like most of the time types are inferred. Similarly to when we have to annotate types because multiple types are possible, there are cases where the lifetimes of references could be related in a few different ways, so Rust needs us to annotate the relationships using generic lifetime parameters so that it can make sure the actual rust single quote used at runtime will definitely be valid.
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. Lifetime annotations have a slightly unusual syntax: the names of lifetime parameters rust single quote start with an apostrophe ', rust single quote.
The names of lifetime parameters are usually all lowercase, and like generic types, their names are usually very short. Said another way, a lifetime approximates the span of execution during which the data a reference points to is rust single quote. The Rust compiler will conservatively infer the shortest lifetime rust single quote to be safe.
If you want to tell the compiler that a reference lives longer than the shortest estimate, you can name it, saying that the output reference, for example, rust single quote, has the same lifetime as a given input reference. The 'static rust single quote is a special lifetime, rust single quote, the longest lived of all lifetimes - for the duration of the program.
You can get more information from this slide deckstarting around slide Lifetimes in Rust also discusses lifetimes in some depth.
To add to quux00's excellent answer, named lifetimes are also used to indicate the origin of a returned borrowed variable to the rust compiler. won't compile because it returns a borrowed value but does not specify whether it borrowed it from a or b.
To fix that, you'd declare a named lifetime and use the same lifetime for b and the return type:. Sign up with email Sign up Sign up with Google Sign up with GitHub Sign up with Facebook. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more.
What are the Rust types denoted with a single apostrophe? Ask Question. Asked 7 years, 4 months ago. Active 7 months ago. Viewed 15k times. I've encountered a number of types in Rust denoted with a single apostrophe: 'static 'r 'a What is the significance of that apostrophe?
edited Oct 29 '17 at Shepmaster k 50 50 gold badges silver badges bronze badges. asked Feb 26 '14 at Greg Malcolm Greg Malcolm 2, 4 4 gold badges 19 19 silver badges 23 23 bronze badges, rust single quote. Add a comment. Active Oldest Votes. These are Rust's named lifetimes. Quoting from The Rust Programming Language : Every reference in Rust has a lifetime, which is the scope for which that reference is valid.
edited Jan 13 '20 at LuxuryMode 32k 34 34 gold badges silver badges bronze badges. answered Feb 26 '14 at quux00 quux00 answered Nov 30 '20 at Nino Filiu Nino Filiu Sign up or log in Sign up using Google.
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Tokens - The Rust Reference
It is better to rust out than wear out. Edwin Markham. Wisdom Better Wear. What I absolutely want is to suggest that before it's anything else, redemption is God mending the bicycle of our souls; God bringing out the puncture repair kit, re-inflating the tires, taking off the rust, making us roadworthy once more API documentation for the Rust `single_quote_char` macro in crate `prolog_parser` So far we’ve worked only with numbers, but Rust supports letters too. Rust’s char type is the language’s most primitive alphabetic type, and the following code shows one way to use it. (Note that char literals are specified with single quotes, as opposed to string literals, which use double quotes
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