On 23/09/13 20:52, Jason Fager wrote:
Doesn't seem like enough bang for the buck to me. In your
first example you save 3 vertical lines but get a really wide one in
return, and lose some indentation levels but add more syntax and
conceptual overhead to the language.
Might be my lack of imagination, but the feature doesn't seem to
expand out to many other use cases, either.
Your second case you could write as:
let foo = get_option("foo");
let bar = get_option("bar");
if foo.is_some() && bar.is_some() {
use(foo.unwrap(), bar.unwrap());
}
It's also possible to write a `matches` macro:
macro_rules! matches {
($e:expr ~ $($p:pat)|*) => {
match $e {
$($p)|* => true,
_ => false
}
}
}
fn main() {
let a = Some(1);
let b = Some(2);
if matches!((a,b) ~ (Some(_), Some(_))) {
println("whatever");
}
}
(This has the drawback that accidentally (or otherwise) using a pattern
that always matches, e.g. `matches!((a,b) ~ (_,_))` gives a error
message about the `_ => false` arm being unreachable, which isn't
particularly intuitive.)
Following the use-more-macros line, one could modify the above to give
something like
if_matches!(foo ~ (Some(a), Some(b)) => {
// use a, b
})
by adding an $expr argument to use instead of `true` and replacing the
false arm with `{}`. Note: this *may* break when match-var-hygiene is
implemented (https://github.com/mozilla/rust/issues/9384), I'm not sure.
Huon
_______________________________________________
Rust-dev mailing list
[email protected]
https://mail.mozilla.org/listinfo/rust-dev
