trait Print {
fn print(&self);
}
struct Printer {
p: Box<Print>,
}
fn main() {
let i = 1i32;
let s = String::from_str("Hello");
// let mp = make_printer!(i,s);
let mp = |i: i32, s: String| {
struct Foo {
i: i32,
s: String,
}
impl Foo {
fn new(i: i32, s: String) -> Foo {
Foo { i: i, s: s }
}
}
impl Print for Foo {
fn print(&self) {
println!("{} {}", self.i, self.s);
}
}
Printer { p: box Foo::new(i, s) }
};
let printer = mp(i, s);
printer.p.print();
}
我想创建make_printer!
宏,如果我用make_printer!(i,s)
调用它,它应该扩展到mp
.
这可能吗?我认为最大的问题是我需要从C++中得到decltype
个这样的东西,这样我就可以从变量中提取类型.然后, struct 可以如下所示:
#![feature(macro_rules)]
macro_rules! make_printer(
($($element:ident),*) => (
struct Foo{
$($element : decltype($element),)*
}
)
)