How to increment CartesianIndex?

[stevengj]

@Ahmed_Salih

I would like it to throw nothing or return the same value when doing 5,5 since it is last element.

Then you can use iterate with CartesianIndices(A):

julia> I = CartesianIndices(A)
CartesianIndices((5, 5))

julia> iterate(I, CartesianIndex(4,1))
(CartesianIndex(5, 1), CartesianIndex(5, 1))

julia> iterate(I, CartesianIndex(5,4))
(CartesianIndex(1, 5), CartesianIndex(1, 5))

julia> iterate(I, CartesianIndex(4,5))
(CartesianIndex(5, 5), CartesianIndex(5, 5))

julia> iterate(I, CartesianIndex(5,5))  # last index, returns nothing

(When it doesn’t return nothing, it returns the same index twice due to the iterate API, but you can just ignore the second return value and the compiler should eliminate it.)