Function op_from_location 

pub fn op_from_location(
    matrix: &[Vec<i64>],
    i: usize,
    j: usize,
) -> Result<ChangeOp>

The change that leads to a cell: music21’s getOpFromLocation – none where the cost standing there is the cheapest move’s, otherwise the cheapest move, up before left before diagonal.

Errors

The origin, which nothing moves onto.