C4 W1 A1 EX4 pool _forward

Can anyone tell me why I am not putting an Integer Scalar?

Maybe “a_pre” is not a valid variable name.

That must mean that (at least) one of the variables you are using to index a_pre is not an integer. We can’t see your logic for setting those variables, so you will have to do the work to figure out which one of those is not an integer and why that happened. Well, we can see how c is determined, so it must be one of the others (vert_start and so forth).