Maybe I phrased that poorly: you can indeed write the loops yourself (without a speed penalty) as advertised, to do things which are hard/ugly/impossible in numpy. But very often you can do this without dropping all the way down to explicit pointer arithmetic, where you'd have to care about base-0/1 and off-by-one errors (again without penalty). This in-between zone is what I was trying to suggest is worth exploring. See for example https://julialang.org/blog/2016/02/iteration for a taste.

Someone more polyglot than I am will have to comment on C++ comparisons.

You can do some pretty interesting things with indexing in Julia: https://julialang.org/blog/2016/02/iteration