How to run clojure program from terminal

Question

I have just begun learning clojure and I'm using the Textmate editor for writing the scripts. However, I am not able to figure out how to run it from the terminal. Like I type the clj filename.clj command but nothing happens. Do I need to include the function name also somewhere because I have a function that takes a number as an argument.

Here is my code that I want to run from the terminal:

(defn next-collatz-num [n]


(if (even? n)
    (quot n 2)
    (inc (* n 3))))

(defn collatz [n]
  (take-while #(< 1 %)(iterate next-collatz-num n)))

(defn max-count-collatz [n]
  (when (> n 0)
    (first
      (reduce
        #(if (> (last %1)(last %2)) %1 %2)
          [1 1] (map #(list % (count (collatz %))) (range 1 (inc n)))))))

(max-count-collatz 999999)

Barry Wark · Accepted Answer · 2016-01-28 19:18:40Z

2

Clojure has a much more interactive environment than just running a whole script at the terminal command prompt.

TL;DR, install leiningen, create a project.clj, then run lean repl.

If you don't want to create a project.clj, or if you're curious how to do it the hard way, read on...

You can start a Clojure read-eval-print-loop (REPL) interactive prompt with

java -cp clojure-1.6.0.jar clojure.main

(download the latest Clojure jar here).

Once you're in the REPL, load the code file:

(load-file "my-script.clj")

Now, you can call the function directly:

(max-count-collatz 5)

If it doesn't work as you'd expect, change the code, save and reload it in the REPL:

(require 'my-script :reload-all)

edited Jan 28, 2016 at 19:18

answered Oct 3, 2014 at 2:10

Barry Wark

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8 Comments

Erica Maine Over a year ago

I don't understand the statement "Once you are in the REPL". How?

Barry Wark Over a year ago

@EricaMaine, use the first line (java -cp clojure-1.6.0.jar clojure.main) at the terminal to launch the Clojure REPL.

Erica Maine Over a year ago

Exception in thread "main" java.lang.NoClassDefFoundError: clojure/main This is what I get when I use that line.

Barry Wark Over a year ago

@EricaMaine this assumes clojure-1.6.0.jar is in the current working directory. If it's not, adjust the path to clojure-1.6.0.jar accordingly. See clojure.org/getting_started for more details.

Rebs Over a year ago

It's best to Install leiningen. Then just run lein repl

|

noisesmith · Accepted Answer · 2014-10-03 13:30:07Z

2

While it is possible to run individual Clojure files using Clojure.jar, one of the best things about Clojure is the leiningen dependency manager and build tool. Creating a project is easy, and for anything more than a single file with no external dependencies, it is a huge improvement over using java and Clojure.jar directly.

answered Oct 3, 2014 at 13:30

noisesmith

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3 Comments

Erica Maine Over a year ago

Hi, in my code in the question, when I type (collatz 7), the result that comes is (7 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2), but it should actually be (7 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1). Why is it missing the 1 at the end?

noisesmith Over a year ago

that's because you call (take-while #(< 1 %) ...) - perhaps you want pos? or (complement zero?) or #(> % 1)

Erica Maine Over a year ago

Hi, I was trying to work with namespaces this time in my clojure code, using ns. So, I have my jar file in the Downloads directory, I created a folder "poker" in the Downloads directory. Inside the "poker folder, I created two clojure files that are dependent on each other, so I also put my jar file inside the poker folder. Now, when I did: java -cp clojure-1.6.0.jar clojure.main It gave me "Permission denied". Why is that?

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