matches.rs

#![feature(macro_rules)]

macro_rules! alternative(
	($in_expr:expr, $pat:pat, $out_true_expr:expr, $out_false_expr:expr) => (
		match $in_expr {
			$pat => $out_true_expr,
			_ => $out_false_expr,
		}
	);
)

macro_rules! is_match(
	($expr:expr, $pat:pat) => (
		alternative!($expr, $pat, true, false)
	);
)

macro_rules! extract(
	($in_expr:expr, $pat:pat, $out_expr:expr) => (
		alternative!($in_expr, $pat, Some($out_expr), None)
	);
)

#[deriving(Show)]
enum Foo {
	FooA,
	FooB(u64)
}


fn main() {
	let x = FooB(17);
	let c = is_match!(x, FooB(15..20));
	let d = extract!(x, FooB(a @ 15..20), a + 3);
	println!("{} {} {}", x, c, d);
}