Macro try_read 

macro_rules! try_read {
    () => { ... };
    ($text:expr) => { ... };
    ($text:expr, $input:expr) => { ... };
}

use text_io::try_read;

let i: i32 = try_read!("The answer: {}!").unwrap();
let i: Result<i32, _> = try_read!("The {}{{}}!", "The answer is 42!".bytes());
assert!(i.is_err());

use text_io::try_read;

let i: Result<i32, _> = try_read!("The answer is {}!", "The answer is 42!".bytes());
assert!(i.is_ok());

let i: Result<i32, _> = try_read!("The {}{{}}!", "The answer is 42!".bytes());
assert!(i.is_err());