Function to_string

tests/test_sparse_vec.rs:52–55

()

#[test]
fn to_string() {
    let (a, _) = create();
    assert_eq!(a.to_string(), "(3, 0.5)(9, 0.75)");
}

fn create() -> (SparseVector, SparseVector) {
    let mut a = SparseVector::new(10);