Check whether an array contains a object

General Usage
1

Suppose I have an array of some objects,

struct Obj
v::Int64
end
o1 = Obj(1)
o2 = Obj(1)
os = [o1]

if use “in” to check if os contains o2

o2 in os

it returns true. Because the “in” operator compares elements by “==”. Is there any built-in function that compares elements with “===” when checking if an array contains an object? Then for

isBelong(os, o2)

it will return false.

2

Note that:

julia> o1 === o2
true

so in your case there would be no difference between == and ===. The o1 and o2 objects are indistinguishable in Julia.

However, if you are looking for in suppoting === comparison use IdDict:

julia> a = [1]
1-element Vector{Int64}:
 1

julia> b = [1]
1-element Vector{Int64}:
 1

julia> d = IdDict([a, b] .=> nothing)
IdDict{Vector{Int64}, Nothing} with 2 entries:
  [1] => nothing
  [1] => nothing

julia> a in keys(d)
true

julia> [1] in keys(d)
false
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4

Thanks for your information!
My bad, I just found if set the struct mutable the two objects will not be equal.

julia> mutable struct Obj
       v::Int64
       end

julia> o1 = Obj(1)
Obj(1)

julia> o2 = Obj(1)
Obj(1)

julia> o1 == o2
false

julia> x = [o1]
1-element Vector{Obj}:
 Obj(1)

julia> o1 in x
true

julia> o2 in x
false
5

== falls back to === if you haven’t implemented isequal for your types IIRC

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