On 4/11/12 10:19 AM, Tim Chevalier wrote:
The '-' prefix means that an argument is passed by move, meaning that
when control passes to the callee, it becomes deinitialized at the
call site. (Obviously, this means the caller has to pass an l-value.)
This does not seem to be documented, and should be.
This is correct, except that it does not require that the caller use an
lvalue. The value is indeed moved from the caller to the callee---and
thus the caller must use a value that they own. If this value is an
lvalue, then the lvalue must be of the sort that it can be deinitialized.
Examples might help:
fn take(-x: int) { ... }
fn give(&x: int) {
take(x); // ERROR: x is not owned by give().
let y = 3;
take(y); // OK
let z = y; // ERROR --- y was given away, can't use it anymore
take(x+2); // OK --- rvalue
}
Moving vs copying is most important for unique values, as a move does
not require that the unique value be cloned.
Niko
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