use mdarray::{view, array, tensor, Slice, Dim, Const, expr::Expression};

// Indexing convention: C_ij <- A_ik * B_kj
fn matmul<D0: Dim, D1: Dim, D2: Dim>(
    a: &Slice<f64, (D0, D1)>,
    b: &Slice<f64, (D1, D2)>,
    c: &mut Slice<f64, (D0, D2)>) {
    for (mut ci, ai) in c.rows_mut().zip(a.rows()) {
        for (aik, bk) in ai.zip(b.rows()) {
            for (cij, bkj) in ci.expr_mut().zip(bk) {
                *cij = aik.mul_add(*bkj, *cij);
            }
        }
    }
}

fn main() {
    let a = view![[1.0, 4.0], [2.0, 5.0], [3.0, 6.0]];
    let b = array![[0.0, 1.0], [1.0, 1.0]];
    let b = b.reshape((Const::<2>, !0));

    // .into_dyn() replaces .reshape(DynRank::from_dims(&[2, 3])).into():
    let mut c: mdarray::Tensor<f64> = tensor![[0.0; 2]; 3].into_dyn();

    dbg!(std::any::type_name_of_val(&a));
    dbg!(std::any::type_name_of_val(&b));
    dbg!(std::any::type_name_of_val(&c));

    matmul(&a.reshape((3, Const::<2>)), &b, &mut c.remap_mut());

    assert_eq!(c, view![[4.0, 5.0], [5.0, 7.0], [6.0, 9.0]]);

    // slice
    let d = a.view(1, ..);
    dbg!(std::any::type_name_of_val(&d));

    // index
    let e = c[4];
    dbg!(std::any::type_name_of_val(&e));

    // permute
    let f = c.permute((1, 0));
    dbg!(std::any::type_name_of_val(&f));
}