How do I skip an iteration of enumerator

General Usage
1

Hi, I have the problem that I have an array which is changing during a loop and I have to skip certain elements.

What is the best way to do this?

a = [1,2,3]
itr = Iterators.Stateful(a)
for (i,el) in enumerate(itr)
    @show el
    if el == 2
        deleteat!(a,i)
        insert!(a,i,9)
        insert!(a,i,8)
        # remove extra iteration
        popfirst!(itr)
    end
end
a

# Output
el = 1
el = 2
el = 3

4-element Array{Int64,1}:
 1
 8
 9
 3
2

Generally Iterators.filter is useful for that, but in this particular case: I don’t think that modifying the underlying vector is allowed (“undefined consequences”).

3

Make a copy of the array to iterate over while you modify the other one? And/or just use a while loop if there’s a clear termination condition.

1 Like
4

I’ll try to use a while loop. If length is calculated every iteration I think it should work.

i = 1
a=[1,2,3]
while i < length(a)

# change length and incr i

i += 1
end
5

Setting a flag to skip the next iteration combined with a continue could also work, I think.

1 Like