I’ve been trying to internalize clojure transducers better of late and I saw this post from Eric Normand. He talks about two ways to “Name your callbacks”.
Option 1: Name the steps
(->> customers
select-best-customers
get-biggest-purchases)
Option 2: Name the callbacks
(->> customers
(filter good-customer?)
(map biggest-purchase))
Like Eric, I prefer the second option but there is another reason to prefer #2. The two statements inside the thread macro ->> can live outside it as transducers. So I can do something like:
(def xf-good-customers (filter good-customer?))
(def xf-biggest-purchases (map biggest-purchase))
(into [] (comp xf-good-customers xf-biggest-purchases) customers)
That will return the same thing and now customers can be anything that transducers will work on (a collection, a async channel, etc.) and I believe it is more efficient.
I suppose you could also rewrite his select-best-customers and get-biggest-purchases function as transducers and get the same thing.