// exru3.ru  declare and use  vector and matrix
    
fn main()
{

  println!("exru3.ru running");
  let mut xs = vec![0, 1, 2];
  println!("Initial xs= {:?}", xs);
  // Insert new element at the end of the vector
  println!("Push 3 onto xs");
  xs.push(3);
  println!("longer xs= {:?}", xs);
  println!("xs length= {}", xs.len());
  println!("xs[2]= {}", xs[2]);
  println!("Pop last element of xs= {:?}", xs.pop());
  println!("xs length= {}", xs.len());

  let n = 3;
  let mut _xt = vec![0.0_f64; n];
  println!("Initial xt= {:?}", _xt);
  println!("xt length= {}", _xt.len());
  _xt[1] = 1.1;
  _xt[2] = 2.2;
  println!("updated xt= {:?}", _xt);
  
  let mut _a = vec![vec![0.0_f64; n]; n];
  println!("initial a= {:?}", _a);
  _a[0][0] = 1.0;
  _a[1][1] = 1.0;
  _a[2][2] = 1.0;
  println!("updated a= {:?}", _a);

  let mut _b = vec![vec![0.0_f64; n]; n];
  _b[0][0] = 2.0;
  _b[1][1] = 2.0;
  _b[2][2] = 2.0;
  println!("updated b= {:?}", _b);
  let mut _c = vec![vec![0.0_f64; n]; n];

  for j in 0..n {  // matrix multiply
    for i in 0..n {
      for k in 0..n {
        _c[i][j] += _a[i][k] * _b[k][j];
      }
    }
  }
  println!("c=a*b= {:?}", _c);

  println!("exru3.ru finished");
}