Avoiding if_ok! repetition with a macro

if_ok_all.rs

#[feature(macro_rules)];

extern mod std;

use std::io::IoResult;

macro_rules! if_ok_all(
    //Note that the Err case in these just returns, b/c this little demo is just running
    //from main and so can't return an IoResult.

    ( $($a:expr <- $e:expr),+ ) => ( 
        { $( $a = match $e { Ok(e) => e, Err(_) => return } );+ }
    );

    ( $($a:ident = $e:expr),+ ) => ( 
        let ( $( $a ),+ ) = ( $(match $e { Ok(e) => e, Err(_) => return }),+ );
    );


)

fn something() -> IoResult<bool> { Ok(true) }
fn something_else() -> IoResult<~str> { Ok(~"hello") }

struct foo {
    a: bool,
    b: ~str
}

fn main() {

    let mut f = foo { a: false, b: ~"" };

    if_ok_all!(
        f.a <- something(),
        f.b <- something_else()
    );

    if_ok_all!(
        a = something(),
        b = something_else()
    );

    println!("{:?}, {:?}, {:?}", f, a, b);
}