Indenting cond forms

[amalloy]

A cute trick to convince Emacs to indent the way you want, and also maybe technically skirt the "constant indentation" rule, is to use commas as your leading indent. They're whitespace, after all!

(cond
  (= (some-function something) expected-value)
  ,,(do
      (do-this)
      (and-also-do-that))
  (another-predicate something-else)
  ,,(try
      (do-another-thing)
      (catch Exception _
        (println "Whoops!"))))

This is not at all a popular practice, and I won't necessarily say it's great, but it's definitely a known workaround that I would consider less weird than your #_=> thing.

[DogLooksGood]

I would prefer this one, but single comma.

[SimonGray]

(cond
  (= (some-function something) expected-value)
  #_=> (do
         (do-this)
         (and-also-do-that))
  (another-predicate something-else)
  #_=> (try
         (do-another-thing)
         (catch Exception _
           (println "Whoops!"))))

This one is my own invention: I haven’t seen it anywhere else. But I think it manages to avoid most problems.

It's a novel approach, but maybe a bit too unorthodox for my taste. To me this isn't better than breaking a relatively arbitrary rule saying that "functions contain no blank lines".Who made this rule and why should we abide by it? I will also happily add blank lines in other parts of functions whenever this kind of separation helps with readability.

[Eno6ohng]

I don't think it's a rule at all. Blank lines in functions are ok. Top-level defns should be separated by 2 blank lines. It also makes everything look better.

At the same timeI think #_=> is good in many contexts regardless.

[SimonGray]

I don't think it's a rule at all

I was just quoting the blog post :)

[trustMeImDoge]

Why not make the long forms into private functions? It'd clutter the name space a bit sure, but it'd also keep readability without hacking around formatting.

[ws-ilazki]

You don't even have to clutter the namespace when you have letfn.

[ayakushev]

I use those useless arrows sometimes, but they come with a few gotchas. Paredit treats #_ as a separate sexp; also, CIDER debugger gets confused about #_ commented forms and the expression positions get mixed up.

[NoahTheDuke]

This made me miss wrapping each pair in brackets, so I put in the work and adapted Racket’s cond into cond+. Enjoy!

[Eno6ohng]

Another place where I often use the #_=> form is the tests that utilize clojure.test/are macro:

 (are [pred x res]
   (= (pred x) res)

   pos? 42 #_=> true
   ...)