Incorrect example in the documentation

[sarahzrf]

This example is incorrect:

reactive-banana/reactive-banana/src/Reactive/Banana/Combinators.hs

Lines 206 to 211 in ee9d5a3

	> mdo
	> let price = 50 :: Int
	> bAmount <- accumB price $ unions
	> [ subtract 10 <$ eCoin
	> , const price <$ eSold ]
	> let eSold = whenE ((<= 0) <$> bAmount) eCoin

I know it's not exactly a bug, but I did lose like 5 minutes puzzling over it because I couldn't see how the code produced the wanted behavior—in fact, it doesn't! The machine does not vend the juice once there's 0 remaining and then reset the cost to 50; it vends it once you insert a coin after there's 0 remaining, resets it to 50, and then credits the new coin. This does produce the behavior of vending after every 5 coins (except for the first time, which requires 6), but it's still a confusing example.

I set up a minimal runnable example for this code and recorded a demo run.

[HeinrichApfelmus]

Ah, I see, because the Behavior still has the value before inserting the coin that should bring it to zero or below. That is an issue, indeed.