Previous lessons have all been focused on teaching our ten- and eight-year-olds some coding, since our six-year-old (Yakov) is still working on reading and writing in English. However, Yakov’s been home sick all week, and he asked me today to teach him some programming. So I came up with a simplified version focused solely on the GHCi prompt.

I started off with:

> x = 32
> x + x

And then I asked him what he thought the answer would be. He quickly came back with 64. Then I typed in:

> y = 5
> x + y

And he got 37 pretty quickly. We played around with a few more bits of simple arithmetic (he hasn’t really mastered multiplication yet). I introduced defining variables in terms of other variables:

> x = 2 * 3
> y = x * 2
> y + 3

This took him a bit longer, but entirely due to the multiplication! This showed me a few things:

1. Reassigning variables was not confusing for him in the least
2. Variable replacement was similarly trivial

Finally, I decided to push things just a bit further and introduce functions:

> f x = x + 3
> f 7

This confused him at first, but once I explained that this was applying the function f to the number 7, he got it, and said “Oh, it’s the +3 function.” (Remember from last time that he’s been playing the function game for a while.) Next, I did:

> x = f 0
> f x

This was easy: it’s 6! Finally, I gave him two more challenging ones:

> f (f 0)
> f (f (f 10))

I fully expected confusion about parentheses. I was shocked: he wasn’t bothered by them at all. He immediately got both answers, and was very proud of himself.

Total time: less than 10 minutes, probably closer to 5. Which is good, because he’s got a short attention span and wanted to play some Nintendo with me, too. Overall, I was very happy with how many concepts he was able to absorb.

(Thanks to my ~/.ghc/ghci_history file for reminding me what we covered today.)