use crate::{macros::sub_matrix::SubMatrix, number::Number};

#[macro_export]
macro_rules! zeros {
  ($e1: expr, $e2: expr) => {{
    use $crate::macros::zeros::Zeros;
    Zeros($e1, $e2)
  }};
}

pub struct Zeros(pub usize, pub usize);

impl<U: Number> SubMatrix<U> for Zeros {
  fn size(&self) -> (usize, usize) {
    (self.0, self.1)
  }

  fn index(&self, _: usize, _: usize) -> U {
    U::default()
  }
}

#[cfg(test)]
mod tests {
  use crate::*;
  #[test]
  fn it_works() {
    let a = mat!(
      1.0, 0.0;
      0.0, 1.0
    );
    assert_eq!(a[(0, 0)], 1.0);
    assert_eq!(a[(0, 1)], 0.0);
    assert_eq!(a[(1, 0)], 0.0);
    assert_eq!(a[(1, 1)], 1.0);

    let b = mat!(
      &a, zeros!(2, 2);
      zeros!(2, 2), &a
    );

    assert_eq!(b[(0, 0)], 1.0);
    assert_eq!(b[(0, 1)], 0.0);
    assert_eq!(b[(3, 0)], 0.0);
    assert_eq!(b[(3, 3)], 1.0);
  }
}