Hashp is a better prn for debugging Clojure code. Inspired by projects like Spyscope, Hashp (ab)uses data readers to make it easier to get useful debugging data sent to STDOUT.

Once installed, you can add #p in front of any form you wish to print:

(ns example.core)

(defn mean [xs]
  (/ (double #p (reduce + xs)) #p (count xs)))

It's faster to type than (prn ...), returns the original result, and produces more useful output by printing the original form, function and line number:

user=> (mean [1 4 5 2])
#p[example.core/mean:4] (reduce + xs) => 12
#p[example.core/mean:4] (count xs) => 4
3.0

Add the following to ~/.lein/profiles.clj:

{:user
 {:dependencies [[hashp "0.2.1"]]
  :injections [(require 'hashp.core)]}}

Add the following to ~/.boot/profile.boot:

(set-env! :dependencies #(conj % '[hashp "0.2.1"]))

(require 'hashp.core)
(boot.core/load-data-readers!)

Add the following to shadow-cljs.edn:

{:dependencies [hashp "0.2.1"]
 :builds {:app {:devtools {:preloads [hashp.core]}}}}

Or alternatively via ~/.shadow-cljs/config.edn and --config-merge:

~/.shadow-cljs/config.edn:

{:dependencies [[hashp "0.2.1"]]}

Run:

shadow-cljs watch app --config-merge '{:devtools {:preloads [hashp.core]}}'

Copyright © 2021 James Reeves

Released under the MIT license.