2018-05-20 Update

I am still going through Clojure For the Brave and True. He does some pretty mind-bending things in chapter 5 when he walks you through his pegthing program.

Check this out:

(defn add-pos
  "Pegs the position and performs connections"
  [board max-pos pos]
  (let [pegged-board (assoc-in board [pos :pegged] true)]
    (reduce (fn [new-board connection-creation-fn]
              (connection-creation-fn new-board max-pos pos))
            pegged-board
            [connect-right connect-down-left connect-down-right])))

In the call to “reduce”, he is sending it a collection of functions called “connect-right”, “connect-down-left” and “connect-down-right”. Then in the function in the reduce, there is a call to “connection-creation-fn”, which is passed to the anonymous function. So he is not actually calling a function called “connection-creation-fn”; that is a placeholder for the functions in the array being passed to “reduce”.

Granted, I knew before this what “reduce” is. But in this chapter he has a lot of functions calling functions. Granted, he does say that reducing over a collection of functions is not something you will do or see very often. Even though I have been looking at Clojure for a while, and this chapter wasn’t really anything new, it was a reminder how different functional programming can be.

You’re welcome.

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