Question

Is the -> operator in Clojure (and what is this operator called in Clojure-speak?) equivalent to the pipeline operator |> in F#? If so, why does it need such a complex macro definition, when (|>) is just defined as

let inline (|>) x f = f x

Or if not, does F#’s pipeline operator exist in Clojure, or how would you define such an operator in Clojure?

Answer 1

No, they are not the same. Clojure doesn’t really have a need for |> because all function calls are enclosed in lists, like (+ 1 2): there’s no magic you could do to make 1 + 2 work in isolation.¹

-> is for reducing nesting and simplifying common patterns. For example:

(-> x (assoc :name "ted") (dissoc :size) (keys))

Expands to

(keys (dissoc (assoc x :name "ted") :size))

The former is often easier to read, because conceptually you’re performing a series of operations on x; the former code is “shaped” that way, while the latter needs some mental unraveling to work out.

¹ You can write a macro that sorta makes this work. The idea is to wrap your macro around the entire source tree that you want to transform, and let it look for |> symbols; it can then transform the source into the shape you want. Hiredman has made it possible to write code in a very Haskell-looking way, with his functional package.