This example show you how to use advanced feature of rust programming language.
use bigint::BigNumber;
fn main(){
let a=BigNumber { mantissa:vec![77,67,13,41],sig:0 };
let b=BigNumber { mantissa:vec![4,6,9],sig: 0 };
let c=a+&b;
let d=BigNumber { mantissa:vec![81,73,22,41],sig:0};
let e=d-&b;
let f=BigNumber { mantissa:vec![77,67,13,41],sig:0 };
let g=BigNumber { mantissa:vec![4,6,9],sig: 0 };
let h=g*&f;
let m=BigNumber { mantissa:vec![4*77,4*67+6*77,4*13+6*67+9*77,4*41+6*13+9*67,6*41+9*13,9*41],sig:0};
println!("{c:?}");
println!("{e:?}");
println!("{h:?}");
println!("{m:?}");
}