map_macro.rs

macro_rules! map {
    () => (::std::collections::HashMap::new());
    
    ($($key: expr => $value: expr),*) => ({
        map!{map!{}, $($key => $value),*}
    });
    
    ($map_instance: expr, $($key: expr => $value: expr),*) => ({
        let mut m = $map_instance;
        $( m.insert($key, $value); )*
        m
    });
}


fn main() {

    let mut m = map!{};
    m.insert("asdf", "fgh");
    println!("Strs: {:?}", m);

    let m = map!{::std::collections::BTreeMap::new(), 5+6 => 11};
    println!("Numbers: {:?}", m);

    let mut m = map!{'a' => 'c'};
    m.insert('d', 'c');
    println!("Chars: {:?}", m);
    
}