linq_macro.rs

macro_rules! linq {
    (from ($from:expr) $fromident:ident select ($($select:expr), +) where ($where:expr)) => {{
        let mut vec = Vec::new();
        for $fromident in &($from) {
            if $where {
                vec.push(( $( $select ), * ));
            }
        }
        vec
    }};
}

struct V {
    val: i32,
    dval: i32,
    sel: bool,
}

fn m_v(a: i32, b: bool) -> V {
    V{val: a, dval: a*2, sel: b}
}

fn main() {
    let v = vec![m_v(1, true), m_v(2, true), m_v(3, false), m_v(4, true), m_v(5, false), m_v(6, false)];
    let v1 = linq!(from (v) m select (m.val, m.dval) where (m.sel == true));
    
    for res in &v1 {
        println!("{:?}", res);
    }
}