Explain the code

[NguyenDuyDuc]

I see this code inside the course:

upper = index - width
if upper > 0:
if costmap[upper] < lethal_cost:
step_cost = orthogonal_step_cost + costmap[upper]/255
neighbors.append([upper, step_cost])

I guess upper = index + 1.

Could you explain it to me, please?

[EnzoGhisoni]

Hi @NguyenDuyDuc,

upper = index - width
if upper > 0:
    if costmap[upper] < lethal_cost:
        step_cost = orthogonal_step_cost + costmap[upper]/255
        neighbors.append([upper, step_cost])

It doesn’t set upper = index + 1 ; instead, it calculates the upper index based on the width of the grid and after checks whether the calculated upper index is greater than 0. It ensures that the upper cell is within the bounds of the grid (assuming the index starts from 0).

[NguyenDuyDuc]

I thought if index = 5, the upper shoud be 6, the left should be 12, top-left is 13, bottom left is 11, and do not have right, top-right and bottom-right?

[EnzoGhisoni]

Hi @NguyenDuyDuc,
Can you post the full code or the location in the course ? It would be easier to explain/understand with more context on the application.