Introduction of Interfaces quite fast

[psteinb]

The following lines from 06-control-flow.md#L44 to 06-control-flow.md#L62 introduce interfaces quite fast.

I think this might put learners off, especially those that come with a background of scripting languages mostly. I personally would encourage to invest some text to introduce the notion of an interface more slowly. Maybe using a number (think interface Real) as an example as discussed in the first episode on typing.

[kescobo]

I agree. In fact, I think the notion of interfaces might be outside the scope of a beginner course. I rarely use interfaces explicitly, and many interfaces in julia are poorly specified.

That said, the array interface is one of the well-specified ones, and pretty fundamental to a lot of science-relevant code. Understanding it can be quite a boon, since many types implement AbstractArray or similar interfaces, and this can allow you to write faster and more generic code.

I definitely think that this section could use a bit more explication, and could be part of a broader re-write of this section (along the lines of #50

[BeastyBlacksmith]

@all-contributors add @psteinb for ideas

[allcontributors]

@BeastyBlacksmith

I've put up a pull request to add @psteinb! 🎉

[BeastyBlacksmith]

@all-contributors add @kescobo for ideas