Shared via Rust Playground

playground.rs

macro_rules! sequence {
    ($x:ident : $t:ty = $init:expr ; $cond:expr ; $change:expr) => {{
        struct Sequence {
            val: $t,
        }
    
        impl Iterator for Sequence {
            type Item = $t;
    
            #[inline]
            fn next(&mut self) -> Option<$t> {
                let $x = self.val;
                if $cond {
                    let old = self.val.clone();
                    let $x = self.val.clone();
                    self.val = $change;
                    Some(old)
                } else {
                    None
                }
            }
        }
        Sequence{val: $init}
    }}
}
fn main() {
    for x in sequence!(x:i32 = 0; x < 10; x + 1) {
        println!("{}", x);
    }
}