Defining an iterator over the fibonacci sequence in Julia.

fibonacciIterable.jl

struct Fibonacci{I}
  first::I
  second::I
end 

function Base.iterate(iter::Fibonacci, state=nothing)
   if state == nothing
       iter.first, (iter.first, nothing)
   elseif state[2] == nothing
       iter.second, (iter.first, iter.second)
   else
       sum(state), (state[2], sum(state))
   end
end

for num in Fibonacci(0, 1)
   println(num)
   sleep(1)
end