I find I don&#x27;t pass individual array indices back and forth between C and Julia as often as I would in Python or Matlab, since I don&#x27;t need as much compiled interface glue. You can do iteration and the like entirely on the Julia side or entirely on the C side and mostly pass the array buffers back and forth. ccall handles that for you if you declare a Ptr{Float64} argument type that the C library expects and send it a Julia Array{Float64} input. It&#x27;s when you have arrays of indices, like the linear programming library his example snippet is referring to, that you notice. Or serializing text-based representations.