[rust-dev] Generic enums : manually implementing Clone trait

Patrick Walton pcwalton at mozilla.com
Mon Apr 21 08:24:33 PDT 2014


On 4/21/14 7:59 AM, José Armando García Sancio wrote:
> On a similar note, why did Rust decide to use the keyword "ref" when
> "borrowing" in those cases and the keyword "&" when borrowing in
> function arguments? Is the semantic different?

`&` in a pattern is the opposite of a reference: it *de*references in 
pattern bindings.

For example

     let &x = &3;

sets `x` to 3 (not `&3`).

This is for symmetry: consider that:

     let (x, y) = (1, 2);

sets `x` to 1 and `y` to 2.

Because `&` is taken to destructure references, we needed another 
keyword to take a reference. Hence, `ref`.

Patrick



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