Usage of `@.`

General Usage
2

@. rand(n) > 0.5 is equivalent to rand.(2) .> 0.5 and not rand(2) .> 0.5. The former is equivalent to

julia> for i in 2
           rand(i) > 0.5
       end

Perhaps you want something like

julia> @. (i -> 2 * (rand() > 0.50) - 1)(1:4)
4-element Vector{Int64}:
 -1
 -1
 -1
 -1

or, more clearly,

julia> [2 * (rand() > 0.50) - 1 for i in 1:4]
4-element Vector{Int64}:
  1
 -1
  1
  1