[legorobot]

> This is a lovely way to look at it!

I wish I had thought of that example too when I wrote about idempotency!

I wrote a post about idempotence as well a couple months back (https://chrisprijic.com/idempotency-is-key/) and use the definition: "its the output + side-effects that should remain the same, regardless of how many times the function with the same input is run".

I had struggled with "on the same input" when I was putting the post together until I thought about how it usually is due to side-effects that idempotency becomes desirable.