type Amount = f64;

trait TObj {
    fn get_name(&self) -> &str;
    fn get_price(&self) -> Amount;
    fn get_qty(&self) -> Amount;

    fn set_qty(&mut self, v: Amount);

    fn amount(&self) -> Amount { self.get_price() * self.get_qty() }

    fn prn(&self) { println!("{} - amount: {}", self.get_name(), self.amount()); }
}

trait TObjTax: TObj {
    fn get_taxrate(&self) -> Amount;

    fn tax(&self) -> Amount { self.amount() * self.get_taxrate() / 100. }

    fn prn(&self) { println!("{} - amount: {}, tax: {}", self.get_name(), self.amount(), self.tax()); }
}

struct Obj {
    name: String,
    price: Amount,
    qty: Amount,
    taxrate: Amount,
}

impl TObj for Obj {
    fn get_name(&self) -> &str { &self.name }
    fn get_price(&self) -> Amount { self.price }
    fn get_qty(&self) -> Amount { self.qty }

    fn set_qty(&mut self, v: Amount) { self.qty = v; }
}

impl TObjTax for Obj {
    fn get_taxrate(&self) -> Amount { self.taxrate }
}

fn main() {
    let mut obj = Obj {
        name: "Веник электрический".to_string(),
        price: 12.3,
        qty: 10.,
        taxrate: 18.,
    };
    TObj::prn(&obj);
    TObjTax::prn(&obj);

    obj.set_qty(50.);
    TObjTax::prn(&obj);
}