Comments on: On Lisp -> Clojure (chapter 2)

By: Sidhant Godiwala

Sidhant Godiwala — Wed, 18 Nov 2009 14:38:32 +0000

Thanks for the link, I've just posted my version of the same chapter and I checked with yours to see what the differences are.

Its really nice to have someone else to compare with and learn from :)

By: Gavin Sinclair

Gavin Sinclair — Tue, 13 Jan 2009 15:39:50 +0000

Nice work. Looking forward to reading the other installments.

By: fogus

fogus — Wed, 01 Oct 2008 19:56:42 +0000

Dan, Thanks for the explanation. I had actually forgotten to go back and L@@k the reason, you saved me some work. ;)

-m

By: Dan

Dan — Wed, 01 Oct 2008 19:36:47 +0000

The reason (sort < '(1 2 3 4 5)) fails is because the < function returns a boolean, not 0, -1 or 1. So if you create a function that follows that requirement:

(defn compare-count [x y]
    (let [x-count (count x) y-count (count y)]
        (cond (> x-count y-count) 1
              (> y-count x-count) -1
              (= x-count y-count) 0)))

then you can use it with sort:

user=> (sort compare-count '([2 2] [5 5 5 5 5] [4 4 4 4] [1] [3 3 3])) ([1] [2 2] [3 3 3] [4 4 4 4] [5 5 5 5 5])

P.S. Hope my formatting comes out okay.

By: fogus

fogus — Tue, 30 Sep 2008 14:58:16 +0000

Excellent post! Far from being discouraged, I am enthusiastic by your recommendations. I am far less interested in being correct than in doing it correctly (if that makes any sense at all).

I was a little discouraged that my implementation of remove-if was 'dangerous' to the stack, and I delighted in your pointers in shoring that up. Thank you. It's clear that I need to study recur more closely.

I am sure that, at least in the early stages, I will make an abomination of the Clojure idioms, but I hope that over time they will become a part of my lexicon.

My initial versions of the the closed counter and make-adderb attempted to use refs, but I couldn't quite get it to work. I will use your advice and attempt to re-implement them, but will most likely keep the old hack laying around as a counter-example/don't-do-this case.

Again, thank you for the tips for this Clojure n00b. -m