Debugging Usages of the Thrush Operator

Creating long chains of transformation using the thrush operator looks attractive, but what if you need to see what it’s doing?

Consider the following code:

(-> 1  
  inc  
  inc)

Now it’s obvious that this returns 3, and that the intermediate value was 2, but the following code proves it:

(defn thread-println [v prefix]  
  (doto v (->> (str prefix) println)))

(-> 1  
  inc  
  (thread-println "Intermediate value was")  
  inc)

You’d need to write a second function for ->>, sadly.