Behaviour of Ref?

New to Julia
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2

Yes, this behavior is expected. Two keywords to look into are mutation and assignment (see for example Assignment and mutation - #4 by StefanKarpinski).

I will add comments to describe:

julia> a = 5 # assign the name `a` to point to the value 5
5

julia> typeof(a)
Int64

julia> b = Ref(a) # assign the name `b` to the value `Ref(a)` which is the exact same thing as `Ref(5)`
Base.RefValue{Int64}(5)

julia> typeof(b)
Base.RefValue{Int64}

julia> b[] = 10 # mutate the contents of `b` to be 10, i.e. perform `setindex!(b, 10)`. 
10

julia> b # observe `b` with its updated contents
Base.RefValue{Int64}(10)

julia> a # the name `a` points to the same, unmutated value, 5, since that value has never been touched
5

Note that Refs are like any other container; they contain values, and you can change their contents by mutating them.

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