Question

Clojure is awesome, we all know this, but that’s not the point. I’m wondering what the idiomatic way of creating and managing higher-order functions in a Haskell-like way is. In Clojure I can do the following:

(defn sum [a b] (+ a b))

But (sum 1) doesn’t return a function: it causes an error. Of course, you can do something like this:

(defn sum
  ([a] (partial + a)) 
  ([a b] (+ a b)))

In this case:

user=> (sum 1)
#<core$partial$fn__3678 clojure.core$partial$fn__3678@1acaf0ed>
user=> ((sum 1) 2)
3

But it doesn’t seem like the right way to proceed. Any ideas?
I’m not talking about implementing the sum function, I’m talking at a higher level of abstraction. Are there any idiomatic patterns to follow? Some macro? Is the best way defining a macro or are there alternative solutions?

Answer 1

Someone has already implememented this on the Clojure group. You can specify how many args a function has, and it will curry itself for you until it gets that many.

The reason this doesn’t happen by default in Clojure is that we prefer variadic functions to auto-curried functions, I suppose.