Comment by wannabe44
19 hours ago
> `fold` is awesome and super useful. It's the easiest and most convenient way to turn a collection into a single value.
You will eventually learn about something called "for loop", and it will be nice.
19 hours ago
> `fold` is awesome and super useful. It's the easiest and most convenient way to turn a collection into a single value.
You will eventually learn about something called "for loop", and it will be nice.
There are way more places where a simple typo will ruin you in a for loop than a reduce or fold or map. Using briefer abstractions in place of nested loops is almost always preferable.
> Using briefer abstractions in place of nested loops is almost always preferable.
Indeed, this is why everyone knows the J programming language.
Nah. It involves multiple passes and setting the answer to the wrong value before (hopefully) setting it to the right value.
Plus it forces you out of whatever lazy/streaming paradigm you had going on. If your foldr produces a list, downstream can start consuming it in constant memory as long as you let it do its thing.
fold kinda does too, for setting the first combined value that you are assembling, and thus on an empty list you end up with that wrong value, same as the for loop
japgolly’s signature for reduce above is slightly wrong, it should be `[A] -> ((A,A) -> A) -> Maybe A`.
I.e. there is no initial value to pass in, but the result is an Optional to handle the empty iterator case. That’s how rust does it, for example:
https://doc.rust-lang.org/std/iter/trait.Iterator.html#metho...
No, the sum of the first ten natural numbers is always 55. It is not "initialised" to some other number beforehand.