Is there an elegant way to do "not in" in Julia?

Question

I am trying to convert a python script to Julia. I am checking to make sure I am doing this code in the most optimal way. Please see the following code:

julia> a = [1,2,3,4,5]
5-element Array{Int64,1}:
 1
 2
 3
 4
 5

julia> if 1 in a
           print("1 is in a")
       end
1 is in a
julia> if 6 not in a
           print("6 not in a")
       end
ERROR: TypeError: non-boolean (Int64) used in boolean context
Stacktrace:
 [1] top-level scope at REPL[6]:1

julia> push!(a, 6)
6-element Array{Int64,1}:
 1
 2
 3
 4
 5
 6
julia> if (6 in a) == true
           print("6 in a")
       end
6 not in a
julia> b = [1]
1-element Array{Int64,1}:
 1

julia> if (6 in b) == true
           print("6 in b")
       end

Am I doing this "not in" check correctly?

Answer 1

julia> a = [1, 2, 3, 4, 5];

julia> 6 ∉ a
true

The ∉ symbol can be typed in the REPL by typing \notin and then hitting TAB. Of course, the ∈ symbol is also available as an alternative to in by typing \in and hitting TAB:

julia> 6 ∈ a
false

Sometimes you need a vectorized version:

julia> x = [2, 7];

julia> x .∉ Ref(a)
2-element BitArray{1}:
 0
 1

The Ref is needed in this case so that a is treated as a scalar in the broadcasting operation.

Edit:

As noted by @SalchiPapa and @DNF in the comments, you can do !(6 in a) if you prefer to avoid Unicode characters.