After reading the recent discussions about lifetime notation, I was
wondering why lifetimes need their own names. Lifetimes refer to
variables that already have names. For example, given this fn from the
borrowed pointers tutorial:
fn select<T>(shape: &Shape, threshold: float,
a: &r/T, b: &r/T) -> &r/T {
if compute_area(shape) > threshold {a} else {b}
}
What does lifetime `r` actually need a name? The return type is
referring to the lifetime of the `a` and `b` parameters. Those
parameters already have names. Is it possible to declare a type that
references a lifetime name that is not in scope? Could the return type
refer to those names (`a` or `b`)? For example:
fn select<T>(shape: &Shape, threshold: float,
a: &T, b: &T) -> &a/T {
if compute_area(shape) > threshold {a} else {b}
}
Regarding syntax, since the lifetime is annotating a type, would a
lifetime suffix be feasible? For example, &T is a "pointer to T" and
&T'lt could be a "pointer to type T with a lifetime of lt"
chris
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