On: Why I love Common Lisp and hate Java (2012)

[servbot]

Here is something from Clojure that stuck with me as particularly elegant:

The -> macro.

  (-> {}
      (add-person 'servbot)
      add-age
      add-info
      add-to-db
      notify-status-by-email
      log-user-addition
  )

So the threading operator is exactly what you ask. It inserts the results of the previous expression as the first argument as the first argument as the next expression. Note this still supports situations where an expression can take more than one argument.

Additionally, there is the ->> operator which inserts the previous result as the last argument in the next expression and some a library that includes the "magic wand" operator "-<>" ala

  (-<> {}
      (add-person 'servbot)
      (add-age 21 <>)
      (add-info 'servbot <> 21)
      (add-to-db 'my-db-handle 5432 <>)
      notify-status-by-email
      (log-user-addition 'dev 'email <> 'paint-by-numbers)
  )

This particular set of macros seems entirely trivial until you use it, and then it changes your entire perspective of what functions do since your ability to express the computation pipeline changes completely.

Edit: Update for formatting.

[luminous_arbour → servbot]

The Clojure standard library has had the the 'as->' macro for a while which serves the same purpose as the "magic wand". It doesn't need to use '<>' as the identifier, but I usually choose to do so because I learned about the magic wand library before I learned about the 'as->' macro.

  (as-> {} <> 
      ...
      (add-age 21 <>)
      ...)