21 ms·

Getting Started With Clojure

279 points by jrheard 14y ago

manishsharan 14y ago
This is a great article. More articles in similar tone are needed to highlight how simple this language is. A big disservice to Clojure was probably done by a few early adopters of Clojure who hyped up the LISP heritage of the language to the extent it turned away C/java guys like myself: I recall reading somewhere that in order to learn Clojure , one had to master SICP and Scheme. That was a huge learning curve I did not have time or inclination for. However, once I waded into Clojure, I was amazed by how simple the language is really and how productive I could get; Clojure REPL is awesome . I still haven't mastered the language, I haven't mastered macros, protocols etc. and I bet my code is ghastly and non-idiomatic but I have still managed to write Clojure code that does what it is supposed to do in a highly concurrent workload.
- dman 14y ago
  This isnt specific to Lisp. There are people who think that learning C++ will help you learn Java, learning C will help you learn C++ etc.
- zorked 14y ago
  Which is why I have been telling people it's a "better Python".
  - pekk 14y ago
    With dramatically different design goals from Python? Even if I like Ruby better than Java, it doesn't make Ruby a better Java because they are doing quite different things.
- Sandman 14y ago
  I had the same experience. When I first heard about Clojure, one of the first things I learned was that it was a Lisp. But having read in numerous comments, blog posts etc. that "only the top percentile of programmers use Lisp", and since I don't consider myself to be anywhere near the top percentile, I felt that my programming chops might not be adequate enough to learn it. So I put off learning Clojure for about a year or so. However, I grew more and more weary of Java's obvious shortcomings, the inherent bureaucratic nature of the language and lack of modern programming features (such was the situation at the time at least, things are starting to look better for Java nowadays) and started to look to other languages. I tried Scala. It didn't work out. I still wanted to leverage my existing knowledge of JVM and the whole Java ecosystem, so I turned to Clojure again. Also, having spent perhaps too much time on HN, I really wanted to see what that fuss about Lisp was all about. Anyway, what I found out was that you do not, in fact, need to be a genius developer to learn Clojure. Actually, Clojure was everything I hoped for. It's dead simple. The syntax is minimal compared to some other languages. You may have heard other people say that learning Lisp can be an enlightening experience. Yes, there definitely are some enlightening moments, but not in the sense that you need to spend years meditating on something to be able to understand it. Read a good book, there are plenty of those around now, watch some of Hickey's talks, and you'll get it. To summarize, here's my message to anybody who is thinking of learning Clojure - don't get discouraged and give up on Clojure before even trying to learn it just because it's a Lisp. It may seem strange and perhaps a little frightening at first, but once you spend some time with it, you'll get amazed at how wonderfully simple it really is, and how powerful it is precisely because of this simplicity.
  - wonderzombie 14y ago
    since I don't consider myself to be anywhere near the top percentile, I felt that my programming chops might not be adequate enough to learn it. See? The magic was within you all along. :) I wonder if the causation is confused, here. That is, you do not need to be a top percentile programmer to understand or use Lisp. You are -- or become -- a top percentile programmer because you've learned Lisp. I don't know if the relationship is as direct as all that. But I do think that if you learn and internalize some of the lessons of Lisp, it will expose you to new ways of thinking about programming as well a programming problems, and this is correlated with being a good programmer. One particular example: the close relationship between code and data in Lisp pulls aside the curtain a bit on some concepts which are more obscured in languages like Java or C++.
    - jwdunne 14y ago
      I don't know about Lisp making me a top-percentile programmer but I do know learning Lisp has improved my skills (not mastering, of course, but becoming comfortable reading & writing code in it). I also feel what I've read from SICP has helped massively too. For one, recursion. I 'got' it as far as the fact it's a function calling itself but it was only through digesting Lisp books, writing lisp and talking about Lisp that I finally got it. SICP helped further with recursive-iterative stuff too - it doesn't just need to call itself to be recursive. Another is functional programming. There are many more but the point is that I could have learned all these concepts, mentioned or not, in other languages but it was the simplicity of Lisp that I feel allowed me to truly understand them. I also feel if I dedicated more time into Lisp, I'd get much more than just a new language out of it.
- brudgers 14y ago
  The reason for the hype may have been to leverage the rich literary tradition of LISP. Understanding LISPiness of Clojure probably depends upon that literature - there just aren't Clojure specific equivalents.
leephillips 14y ago
At first the Clojure environment is confusing: why do I need Leiningen? How do I use libraries in my project? This article is a good place to start for beginners, as it explains all that.
wonderzombie 14y ago
I knew about clojars.org, but I hadn't known about http://www.clojure-toolbox.com/ http://www.clojure-toolbox.com/. Very nice! I also recommend the Value of Values video presentation: http://www.infoq.com/presentations/Value-Values http://www.infoq.com/presentations/Value-Values. It will help you internalize Clojure's approach to data. I really wish I could remember why I didn't experience nearly as much pain starting out as the author, but I'm glad that he took the trouble to put this together.
- jrheard 14y ago
  That talk's definitely a good one. I particularly like how he frames it as a discussion about the difference between value-oriented programming (good) and place-oriented programming (what you're used to, bad). Giving the two paradigms those names really helps clarify how you think about the distinctions between the two.
- graue 14y ago
  Off topic perhaps, but is Rich Hickey's wisdom only summarized in talks, or has he written some of this down? I see a number of glowing reviews of videos like this. While I don't want to miss out, I would personally much rather consume this info in writing. The one I did bite the bullet on and watch in full was his talk on “hammock-driven development”. I liked it, but couldn't help feeling it would have made a very nice blog post that I could've read in 5 to 10 minutes as opposed to watching a 30 minute video.
  - jrheard 14y ago
    I really suggest biting the bullet on "are we there yet" - it changed the way I think about state and identity (in that it got me to start thinking about them at all). I haven't found anything by him in written form aside from interviews, though, but I'm still really new here.
  - fogus 14y ago
    While 'Joy of Clojure'[1] can in no way be considered "the way Rich thinks", we have tried very hard to capture the Clojure philosophy as we understand it. This is based on personal interactions with Rich, his talks, the Clojure and Clojure implementations, Datomic, IRC chats and experience using the language every day. [1]: http://www.joyofclojure.com http://www.joyofclojure.com
scarmig 14y ago
Very nice, JR, best guide I've seen. I've always wished, though, that all "getting started" guides would just provide a chef recipe or machine image with everything ready to go. Getting to know a language shouldn't require jumping through an hour of hoops and documentation to get it set up. (Of course, the guide here is broader than simply getting your system set up.)
- michaelsbradley 14y ago
  Thanks to Leiningen[1], getting started with Clojure is super simple. It doesn't get much easier than pulling down the master `lein` script (or `lein.bat` for Windows) with wget/curl and setting it up on your PATH as an executable. This is similar to rvm[2], nvm[3], perlbrew[4], et al. You'll need to have Java installed before proceeding to the next step. Once you've done that, you can run `lein repl` in your shell -- Leiningen will bootstrap itself when it's run for the first time, and when it's done you'll be presented with a Clojure REPL. Now you're ready to start exploring and learning: http://clojure.github.com/clojure/ http://clojure.github.com/clojure/ http://clojuredocs.org/ http://clojuredocs.org/ http://clojure-doc.org/ http://clojure-doc.org/ Also, please join the friendly community in #clojure on irc.freenode.net[5]. You'll find folks in there nearly 24/7 who are willing to answer questions you may have as you learn your way around. The discussion group[6] is also a great resource. [1] http://leiningen.org/#install http://leiningen.org/#install [2] https://rvm.io/ https://rvm.io/ [3] https://github.com/creationix/nvm https://github.com/creationix/nvm [4] http://perlbrew.pl/ http://perlbrew.pl/ [5] http://webchat.freenode.net/?channels=clojure http://webchat.freenode.net/?channels=clojure [6] http://groups.google.com/group/clojure http://groups.google.com/group/clojure
  - chc 14y ago
    I wanted to get Clojure on my secondary machine to do a little light fiddling, but as it turns out, Windows doesn't include wget or curl, and lein.bat requires those. So I have to download something that requires me to download something so I can download something that will let me install the thing I wanted in the first place. I think it could be a bit easier.
politician 14y ago
I hope the Light Table guys see this article and incorporate the guide into their OOBE content. hint, hint ;)
dschiptsov 14y ago
The same thing could be done in Python (with requests) and Ruby (with whatever-it-is) with more clarity, less confusion, and much less consumption of resources.) (:headers resp) This construction is confusing - it breaks environmental model (scoping) and general evaluation rule of Lisps - is :headers a global symbol? a part of foo namespace? Is it macros? (resp :headers) On the other hand, this form is perfectly consistent - I'm sending to some closure which is bound in a global or other environment a constant message. The assumption that the reader function implicitly transforms first form to second is of no good, because it is not obvious and breaks intuition about environments and violates principle of less astonishment. That thing (:headers resp) returned - what language is it?)
- wtetzner 14y ago
  >This construction is confusing - it breaks environmental model (scoping) and general evaluation rule - is :headers a global symbol? a part of foo namespace? Is it macros? It follows Clojure's evaluation rules just fine: it's an object that implements the IFn interface. > On the other hand, this form is perfectly consistent - I'm sending to some closure which is bound in a global or other environment a constant message. resp isn't a closure, it's a map, which is also an object that implements IFn.
  - dschiptsov 14y ago
    How could you tell this from the code?)
    - wtetzner 14y ago
      You can tell by knowing Clojure. Things that start with : are keywords, and keywords implement IFn.
    - prospero 14y ago
      Because keywords are functions which are implemented such that: (:keyword m) calls in turn (get m :keyword) That's just a basic feature of the language. No macros involved.
DigitalJack 14y ago
I didn't know about clojure-toolbox. That's pretty neat. One thing though, regarding this page, is that you don't need to install clojure with brew. Leiningen takes care of all that... clojure is just a jar that's included in your project, aka a dependency, and Leiningen manages that. This lets you tie a specific version of clojure to that project, which is handy for some legacy projects that aren't maintained anymore. Also, if you drop the brew references, then this becomes OS agnostic. Just go to the leiningen page on github[1] and it'll get you started: osx, windows, linux. I develop with clojure on my mac and I've not brewed anything related to clojure. [1] https://github.com/technomancy/leiningen https://github.com/technomancy/leiningen
- babs474 14y ago
  This is something that clojure got right before any other language I'm familiar with did. You do not "install" clojure. You depend on clojure just like you might log4j or joda-time
  - matthavener 14y ago
    You still need to install the JVM. Python/perl/ruby require installers because you need some platform-specific stuff for each. Running everything inside the JVM means you only need to ship what any arbitrary JVM library requires. In this case, its as simple as a .jar.
    - babs474 14y ago
      True clojure assumes the existence of the JVM. However no other jvm language has gone with the language as library system which is a shame. Also, I don't think anything would preclude non jvm hosted languages from doing something similar. I think it is a better solution than say virtualenv from python.
      - eeperson 14y ago
        I believe that is what all of the other JVM languages do. How is what Clojure does any different that what Scala or Groovy does?
spacemanaki 14y ago
> The reason that you won’t find yourself running `clj` often is that the REPL built into bare Clojure is pretty much garbage.... This is what rlwrap is for. Call `rlwrap clj` instead of `clj`, and you get all that and more (C-r, for reverse incremental search, etc). Works with every other REPL that doesn't bother to re-implement read-line.
- vutekst 14y ago
  Using a raw repl at all is painful compared to just selectively evaluating expressions from a buffer (say, in Emacs, VimClojure, or the Eclipse and IntelliJ plugins).
  - wonderzombie 14y ago
    I must second this. You can get used to it, and I did. For a while, I used Vim or ST2 + a terminal window with lein repl. As of a week or so ago, I started using Emacs with Clojure & nrepl. Aside from the occasional teething problems (still not used to the Emacs paradigm), it's amazing. Merely having the REPL in a text-editor-like buffer is a big win, and there's a bunch more that I'm still incorporating into my workflow.
  - emidln 14y ago
    I use this for clojure's python port with vim. I just sit inside vim and have macros that can evaluate the buffer or a selection thereof.
  - spacemanaki 14y ago
    I agree! Anyone who ends up using Clojure more than a little bit will figure out how to use them, I'm sure. But rlwrap is still a very useful tool because it works with every REPL. It will always be there, for those first sessions when you start learning a new language, or when you just need to answer some question about a language you rarely use, or when you write your own interpreter and don't want to also write read-line or an Emacs inferior-foo-mode.
- cgag 14y ago
  Install rlwrap, but then just always stick to `lein repl`. It's pretty rare to ever need to run Clojure without lein.
technomancy 14y ago
I wish people would at least attempt contributing to official documentation instead of spreading stuff across random blogs.
- jrheard 14y ago
  Fair point, mea culpa :) I'll carve out some time this weekend, figure out how to make this advice generic across platforms, and figure out how to contribute it to dev.clojure.org.
  - jkkramer 14y ago
    Please do. Good writers like yourself can make a big difference right now. There's also the Clojure Doc project - http://clojure-doc.org/ http://clojure-doc.org/
    - jarifikwa 14y ago
      I am a mediocre-at-best Java developer, but somewhat better at writing. I'd like to learn Clojure and contribute to the community while doing so. Is the Clojure Doc project the best opportunity for someone like me?
      - jkkramer 14y ago
        Clojure Doc is easier since it doesn't require a CA. IRC (#clojure and #clojure-doc on Freenode) is good for coordinating with other contributors.
147 14y ago
Anybody have any ideas for beginner projects in Clojure?
- kybernetyk 14y ago
  I've written a blog-system in it mainly because I'll be using Clojure for web development and blogs are the hello worlds of webdev.
- khill 14y ago
  Not necessarily a project but a good way to learn is using 4clojure: http://www.4clojure.com/ http://www.4clojure.com/
pandeiro 14y ago
or, # make sure you have java/open-jdk already wget https://raw.github.com/technomancy/leiningen/preview/bin/lein && chmod +x lein && ./lein repl
tesmar2 14y ago
I have been thinking about getting into Clojure, but time is precious. It doesn't seem like there are that many jobs out there, but I could be wrong. For those of you in the industry, why would I want to use Clojure? What would be a good project to try it on? A Web app? Why is it worth learning it?
- paolovictor 14y ago
  This post is specially relevant for me, since last weekend I've decided to take a quick look at Clojure, as one of my personal goals this year is to get acquainted with a Lisp dialect. From my _very_ short experience (I've started coding a simple game), here are my two cents: - If your application is heavily dependent on state, which changes continuously and must be maintained during most of the execution time - like a game - it may not be a good fit. You'll waste a lot of working around the fact that each modification results on new objects. - If your application comprises mainly of short requests that may create some state that will most certainly be discarded shortly after - like a web application - then I think it's a good fit and you'll probably enjoy it better. Once again, I've just got started with it, so take this with a grain of salt :)
  - tesmar2 14y ago
    Thanks for this. I'd hate to start down the road of writing a game in clojure.... I may try the blog/webapp idea with Clojure.
    - jrheard 14y ago
      Programming a game in Clojure might not be such a bad idea - mikera has some really great thoughts at http://stackoverflow.com/questions/9755882/are-functional-programming-languages-suitable-for-graphics-programming http://stackoverflow.com/questions/9755882/are-functional-pr... . Also, you might find this series of blog posts interesting: http://briancarper.net/blog/520/making-an-rpg-in-clojure-part-one-of-many http://briancarper.net/blog/520/making-an-rpg-in-clojure-par...
      - 14y ago
tripzilch 14y ago
Shouldn't the title say "Getting Started With Clojure in OSX"?
gits1225 14y ago
"When I was going through all this myself a few months back, there was a weird period of a good few weeks when I had basically no mental map of the Clojure ecosystem and had no idea how to assemble one." One of the things you can do when learning something new is to hop onto IRC and join a channel related to the topic. I almost always have got a good overview of things just by asking around what I am supposed to know.
dizzystar 14y ago
I wish someone would do a Learn Clojure the Hard Way. The comments in this thread is a great documentation of the unfounded fears of the language. I also want to point out to those who are using Windows: Yeah, you could, but this is not a good idea. Leiningen 2 is not available for Windows, but you can still get quite a bit done. At some point, you just have to bite the bullet and install a VM with Linux to really dive into it.
- DigitalJack 14y ago
  Leiningen 2 is absolutely available on windows. And clojure on windows is the same as clojure on any other platform. That's the beauty of running on the JVM. Light Table has a windows client; Eclipse with the counterclockwise plugin (a leiningen/clojure plugin) runs great on windows; running from the command prompt works great on windows. I agree though, that a "Learn Clojure The Hard Way" a la Shaw would be nice.
  - dizzystar 14y ago
    Really? The only thing I get when I attempt to install Lein2 on Windows is "This is not available on Windows." Running Windows 7 Home. I'm not a huge fan of using a bunch of IDEs and just use Emacs. After a year of fighting with Windows, I got fed up with it and installed Linux with a VM and now everything works like a dream. EDIT TO ADD: I would love to do a project like Learn Clojure the Hard Way, but I'm simply not confident in my abilities to do it correctly. I've written some pretty significant programs in Clojure (see my profile), but I wouldn't be able to solve but a few Project Eulers with it. I'm simply too new at programming in general.
    - DigitalJack 14y ago
      I'm a Mac person myself, but use windows for work and have leiningen and clojure running fine. I just used the batch file from the leiningen github to get up and running on windows. Someone else brought up the point that lein needs wget or curl, and that isn't something that is installed by default on windows. I happened to already have them, so I never thought much about it. GNU has a version of wget and maybe curl too for win32. And there is always cygwin if you like. https://github.com/technomancy/leiningen https://github.com/technomancy/leiningen http://gnuwin32.sourceforge.net/packages/wget.htm http://gnuwin32.sourceforge.net/packages/wget.htm
paddyoloughlin 14y ago
I'm interested in learning LISP. How good a choice is learning Clojure as a way of achieving this? I've read a page[1] listing differences between Clojure and other LISPs, but I'm not sure that I fully understand the implications of these differences. [1] http://clojure.org/lisps http://clojure.org/lisps
- jrheard 14y ago
  Clojure's a great lisp. I recommend it highly. I haven't spent much time with Scheme, but I can definitely say that I greatly prefer Clojure to Common Lisp.
jumanjisama 14y ago
http://youtu.be/VVd4ow-ZcX0 http://youtu.be/VVd4ow-ZcX0 this video by Chas Emerick (co-author of clojure programming) also gives a good introduction to start with clojure, especially for people who uses eclipse.

279 points by jrheard 14y ago

This is a great article. More articles in similar tone are needed to highlight how simple this language is. A big disservice to Clojure was probably done by a few early adopters of Clojure who hyped up the LISP heritage of the language to the extent it turned away C/java guys like myself: I recall reading somewhere that in order to learn Clojure , one had to master SICP and Scheme. That was a huge learning curve I did not have time or inclination for. However, once I waded into Clojure, I was amazed by how simple the language is really and how productive I could get; Clojure REPL is awesome . I still haven't mastered the language, I haven't mastered macros, protocols etc. and I bet my code is ghastly and non-idiomatic but I have still managed to write Clojure code that does what it is supposed to do in a highly concurrent workload.

dman 14y ago
This isnt specific to Lisp. There are people who think that learning C++ will help you learn Java, learning C will help you learn C++ etc.
zorked 14y ago
Which is why I have been telling people it's a "better Python".
- pekk 14y ago
  With dramatically different design goals from Python? Even if I like Ruby better than Java, it doesn't make Ruby a better Java because they are doing quite different things.
Sandman 14y ago
I had the same experience. When I first heard about Clojure, one of the first things I learned was that it was a Lisp. But having read in numerous comments, blog posts etc. that "only the top percentile of programmers use Lisp", and since I don't consider myself to be anywhere near the top percentile, I felt that my programming chops might not be adequate enough to learn it. So I put off learning Clojure for about a year or so. However, I grew more and more weary of Java's obvious shortcomings, the inherent bureaucratic nature of the language and lack of modern programming features (such was the situation at the time at least, things are starting to look better for Java nowadays) and started to look to other languages. I tried Scala. It didn't work out. I still wanted to leverage my existing knowledge of JVM and the whole Java ecosystem, so I turned to Clojure again. Also, having spent perhaps too much time on HN, I really wanted to see what that fuss about Lisp was all about. Anyway, what I found out was that you do not, in fact, need to be a genius developer to learn Clojure. Actually, Clojure was everything I hoped for. It's dead simple. The syntax is minimal compared to some other languages. You may have heard other people say that learning Lisp can be an enlightening experience. Yes, there definitely are some enlightening moments, but not in the sense that you need to spend years meditating on something to be able to understand it. Read a good book, there are plenty of those around now, watch some of Hickey's talks, and you'll get it. To summarize, here's my message to anybody who is thinking of learning Clojure - don't get discouraged and give up on Clojure before even trying to learn it just because it's a Lisp. It may seem strange and perhaps a little frightening at first, but once you spend some time with it, you'll get amazed at how wonderfully simple it really is, and how powerful it is precisely because of this simplicity.
- wonderzombie 14y ago
  since I don't consider myself to be anywhere near the top percentile, I felt that my programming chops might not be adequate enough to learn it. See? The magic was within you all along. :) I wonder if the causation is confused, here. That is, you do not need to be a top percentile programmer to understand or use Lisp. You are -- or become -- a top percentile programmer because you've learned Lisp. I don't know if the relationship is as direct as all that. But I do think that if you learn and internalize some of the lessons of Lisp, it will expose you to new ways of thinking about programming as well a programming problems, and this is correlated with being a good programmer. One particular example: the close relationship between code and data in Lisp pulls aside the curtain a bit on some concepts which are more obscured in languages like Java or C++.
  - jwdunne 14y ago
    I don't know about Lisp making me a top-percentile programmer but I do know learning Lisp has improved my skills (not mastering, of course, but becoming comfortable reading & writing code in it). I also feel what I've read from SICP has helped massively too. For one, recursion. I 'got' it as far as the fact it's a function calling itself but it was only through digesting Lisp books, writing lisp and talking about Lisp that I finally got it. SICP helped further with recursive-iterative stuff too - it doesn't just need to call itself to be recursive. Another is functional programming. There are many more but the point is that I could have learned all these concepts, mentioned or not, in other languages but it was the simplicity of Lisp that I feel allowed me to truly understand them. I also feel if I dedicated more time into Lisp, I'd get much more than just a new language out of it.
brudgers 14y ago
The reason for the hype may have been to leverage the rich literary tradition of LISP. Understanding LISPiness of Clojure probably depends upon that literature - there just aren't Clojure specific equivalents.

leephillips 14y ago

At first the Clojure environment is confusing: why do I need Leiningen? How do I use libraries in my project? This article is a good place to start for beginners, as it explains all that.

wonderzombie 14y ago

I knew about clojars.org, but I hadn't known about http://www.clojure-toolbox.com/ http://www.clojure-toolbox.com/. Very nice! I also recommend the Value of Values video presentation: http://www.infoq.com/presentations/Value-Values http://www.infoq.com/presentations/Value-Values. It will help you internalize Clojure's approach to data. I really wish I could remember why I didn't experience nearly as much pain starting out as the author, but I'm glad that he took the trouble to put this together.

jrheard 14y ago
That talk's definitely a good one. I particularly like how he frames it as a discussion about the difference between value-oriented programming (good) and place-oriented programming (what you're used to, bad). Giving the two paradigms those names really helps clarify how you think about the distinctions between the two.
graue 14y ago
Off topic perhaps, but is Rich Hickey's wisdom only summarized in talks, or has he written some of this down? I see a number of glowing reviews of videos like this. While I don't want to miss out, I would personally much rather consume this info in writing. The one I did bite the bullet on and watch in full was his talk on “hammock-driven development”. I liked it, but couldn't help feeling it would have made a very nice blog post that I could've read in 5 to 10 minutes as opposed to watching a 30 minute video.
- jrheard 14y ago
  I really suggest biting the bullet on "are we there yet" - it changed the way I think about state and identity (in that it got me to start thinking about them at all). I haven't found anything by him in written form aside from interviews, though, but I'm still really new here.
- fogus 14y ago
  While 'Joy of Clojure'[1] can in no way be considered "the way Rich thinks", we have tried very hard to capture the Clojure philosophy as we understand it. This is based on personal interactions with Rich, his talks, the Clojure and Clojure implementations, Datomic, IRC chats and experience using the language every day. [1]: http://www.joyofclojure.com http://www.joyofclojure.com

scarmig 14y ago

Very nice, JR, best guide I've seen. I've always wished, though, that all "getting started" guides would just provide a chef recipe or machine image with everything ready to go. Getting to know a language shouldn't require jumping through an hour of hoops and documentation to get it set up. (Of course, the guide here is broader than simply getting your system set up.)

michaelsbradley 14y ago
Thanks to Leiningen[1], getting started with Clojure is super simple. It doesn't get much easier than pulling down the master `lein` script (or `lein.bat` for Windows) with wget/curl and setting it up on your PATH as an executable. This is similar to rvm[2], nvm[3], perlbrew[4], et al. You'll need to have Java installed before proceeding to the next step. Once you've done that, you can run `lein repl` in your shell -- Leiningen will bootstrap itself when it's run for the first time, and when it's done you'll be presented with a Clojure REPL. Now you're ready to start exploring and learning: http://clojure.github.com/clojure/ http://clojure.github.com/clojure/ http://clojuredocs.org/ http://clojuredocs.org/ http://clojure-doc.org/ http://clojure-doc.org/ Also, please join the friendly community in #clojure on irc.freenode.net[5]. You'll find folks in there nearly 24/7 who are willing to answer questions you may have as you learn your way around. The discussion group[6] is also a great resource. [1] http://leiningen.org/#install http://leiningen.org/#install [2] https://rvm.io/ https://rvm.io/ [3] https://github.com/creationix/nvm https://github.com/creationix/nvm [4] http://perlbrew.pl/ http://perlbrew.pl/ [5] http://webchat.freenode.net/?channels=clojure http://webchat.freenode.net/?channels=clojure [6] http://groups.google.com/group/clojure http://groups.google.com/group/clojure
- chc 14y ago
  I wanted to get Clojure on my secondary machine to do a little light fiddling, but as it turns out, Windows doesn't include wget or curl, and lein.bat requires those. So I have to download something that requires me to download something so I can download something that will let me install the thing I wanted in the first place. I think it could be a bit easier.

politician 14y ago

I hope the Light Table guys see this article and incorporate the guide into their OOBE content. hint, hint ;)

dschiptsov 14y ago

The same thing could be done in Python (with requests) and Ruby (with whatever-it-is) with more clarity, less confusion, and much less consumption of resources.) (:headers resp) This construction is confusing - it breaks environmental model (scoping) and general evaluation rule of Lisps - is :headers a global symbol? a part of foo namespace? Is it macros? (resp :headers) On the other hand, this form is perfectly consistent - I'm sending to some closure which is bound in a global or other environment a constant message. The assumption that the reader function implicitly transforms first form to second is of no good, because it is not obvious and breaks intuition about environments and violates principle of less astonishment. That thing (:headers resp) returned - what language is it?)

wtetzner 14y ago
>This construction is confusing - it breaks environmental model (scoping) and general evaluation rule - is :headers a global symbol? a part of foo namespace? Is it macros? It follows Clojure's evaluation rules just fine: it's an object that implements the IFn interface. > On the other hand, this form is perfectly consistent - I'm sending to some closure which is bound in a global or other environment a constant message. resp isn't a closure, it's a map, which is also an object that implements IFn.
- dschiptsov 14y ago
  How could you tell this from the code?)
  - wtetzner 14y ago
    You can tell by knowing Clojure. Things that start with : are keywords, and keywords implement IFn.
  - prospero 14y ago
    Because keywords are functions which are implemented such that: (:keyword m) calls in turn (get m :keyword) That's just a basic feature of the language. No macros involved.

DigitalJack 14y ago

I didn't know about clojure-toolbox. That's pretty neat. One thing though, regarding this page, is that you don't need to install clojure with brew. Leiningen takes care of all that... clojure is just a jar that's included in your project, aka a dependency, and Leiningen manages that. This lets you tie a specific version of clojure to that project, which is handy for some legacy projects that aren't maintained anymore. Also, if you drop the brew references, then this becomes OS agnostic. Just go to the leiningen page on github[1] and it'll get you started: osx, windows, linux. I develop with clojure on my mac and I've not brewed anything related to clojure. [1] https://github.com/technomancy/leiningen https://github.com/technomancy/leiningen

babs474 14y ago
This is something that clojure got right before any other language I'm familiar with did. You do not "install" clojure. You depend on clojure just like you might log4j or joda-time
- matthavener 14y ago
  You still need to install the JVM. Python/perl/ruby require installers because you need some platform-specific stuff for each. Running everything inside the JVM means you only need to ship what any arbitrary JVM library requires. In this case, its as simple as a .jar.
  - babs474 14y ago
    True clojure assumes the existence of the JVM. However no other jvm language has gone with the language as library system which is a shame. Also, I don't think anything would preclude non jvm hosted languages from doing something similar. I think it is a better solution than say virtualenv from python.
    - eeperson 14y ago
      I believe that is what all of the other JVM languages do. How is what Clojure does any different that what Scala or Groovy does?

spacemanaki 14y ago

> The reason that you won’t find yourself running `clj` often is that the REPL built into bare Clojure is pretty much garbage.... This is what rlwrap is for. Call `rlwrap clj` instead of `clj`, and you get all that and more (C-r, for reverse incremental search, etc). Works with every other REPL that doesn't bother to re-implement read-line.

vutekst 14y ago
Using a raw repl at all is painful compared to just selectively evaluating expressions from a buffer (say, in Emacs, VimClojure, or the Eclipse and IntelliJ plugins).
- wonderzombie 14y ago
  I must second this. You can get used to it, and I did. For a while, I used Vim or ST2 + a terminal window with lein repl. As of a week or so ago, I started using Emacs with Clojure & nrepl. Aside from the occasional teething problems (still not used to the Emacs paradigm), it's amazing. Merely having the REPL in a text-editor-like buffer is a big win, and there's a bunch more that I'm still incorporating into my workflow.
- emidln 14y ago
  I use this for clojure's python port with vim. I just sit inside vim and have macros that can evaluate the buffer or a selection thereof.
- spacemanaki 14y ago
  I agree! Anyone who ends up using Clojure more than a little bit will figure out how to use them, I'm sure. But rlwrap is still a very useful tool because it works with every REPL. It will always be there, for those first sessions when you start learning a new language, or when you just need to answer some question about a language you rarely use, or when you write your own interpreter and don't want to also write read-line or an Emacs inferior-foo-mode.
cgag 14y ago
Install rlwrap, but then just always stick to `lein repl`. It's pretty rare to ever need to run Clojure without lein.

technomancy 14y ago

I wish people would at least attempt contributing to official documentation instead of spreading stuff across random blogs.

jrheard 14y ago
Fair point, mea culpa :) I'll carve out some time this weekend, figure out how to make this advice generic across platforms, and figure out how to contribute it to dev.clojure.org.
- jkkramer 14y ago
  Please do. Good writers like yourself can make a big difference right now. There's also the Clojure Doc project - http://clojure-doc.org/ http://clojure-doc.org/
  - jarifikwa 14y ago
    I am a mediocre-at-best Java developer, but somewhat better at writing. I'd like to learn Clojure and contribute to the community while doing so. Is the Clojure Doc project the best opportunity for someone like me?
    - jkkramer 14y ago
      Clojure Doc is easier since it doesn't require a CA. IRC (#clojure and #clojure-doc on Freenode) is good for coordinating with other contributors.

147 14y ago

Anybody have any ideas for beginner projects in Clojure?

kybernetyk 14y ago
I've written a blog-system in it mainly because I'll be using Clojure for web development and blogs are the hello worlds of webdev.
khill 14y ago
Not necessarily a project but a good way to learn is using 4clojure: http://www.4clojure.com/ http://www.4clojure.com/

pandeiro 14y ago

or, # make sure you have java/open-jdk already wget https://raw.github.com/technomancy/leiningen/preview/bin/lein && chmod +x lein && ./lein repl

tesmar2 14y ago

I have been thinking about getting into Clojure, but time is precious. It doesn't seem like there are that many jobs out there, but I could be wrong. For those of you in the industry, why would I want to use Clojure? What would be a good project to try it on? A Web app? Why is it worth learning it?

paolovictor 14y ago
This post is specially relevant for me, since last weekend I've decided to take a quick look at Clojure, as one of my personal goals this year is to get acquainted with a Lisp dialect. From my _very_ short experience (I've started coding a simple game), here are my two cents: - If your application is heavily dependent on state, which changes continuously and must be maintained during most of the execution time - like a game - it may not be a good fit. You'll waste a lot of working around the fact that each modification results on new objects. - If your application comprises mainly of short requests that may create some state that will most certainly be discarded shortly after - like a web application - then I think it's a good fit and you'll probably enjoy it better. Once again, I've just got started with it, so take this with a grain of salt :)
- tesmar2 14y ago
  Thanks for this. I'd hate to start down the road of writing a game in clojure.... I may try the blog/webapp idea with Clojure.
  - jrheard 14y ago
    Programming a game in Clojure might not be such a bad idea - mikera has some really great thoughts at http://stackoverflow.com/questions/9755882/are-functional-programming-languages-suitable-for-graphics-programming http://stackoverflow.com/questions/9755882/are-functional-pr... . Also, you might find this series of blog posts interesting: http://briancarper.net/blog/520/making-an-rpg-in-clojure-part-one-of-many http://briancarper.net/blog/520/making-an-rpg-in-clojure-par...
    - 14y ago

tripzilch 14y ago

Shouldn't the title say "Getting Started With Clojure in OSX"?

gits1225 14y ago

"When I was going through all this myself a few months back, there was a weird period of a good few weeks when I had basically no mental map of the Clojure ecosystem and had no idea how to assemble one." One of the things you can do when learning something new is to hop onto IRC and join a channel related to the topic. I almost always have got a good overview of things just by asking around what I am supposed to know.

dizzystar 14y ago

I wish someone would do a Learn Clojure the Hard Way. The comments in this thread is a great documentation of the unfounded fears of the language. I also want to point out to those who are using Windows: Yeah, you could, but this is not a good idea. Leiningen 2 is not available for Windows, but you can still get quite a bit done. At some point, you just have to bite the bullet and install a VM with Linux to really dive into it.

DigitalJack 14y ago
Leiningen 2 is absolutely available on windows. And clojure on windows is the same as clojure on any other platform. That's the beauty of running on the JVM. Light Table has a windows client; Eclipse with the counterclockwise plugin (a leiningen/clojure plugin) runs great on windows; running from the command prompt works great on windows. I agree though, that a "Learn Clojure The Hard Way" a la Shaw would be nice.
- dizzystar 14y ago
  Really? The only thing I get when I attempt to install Lein2 on Windows is "This is not available on Windows." Running Windows 7 Home. I'm not a huge fan of using a bunch of IDEs and just use Emacs. After a year of fighting with Windows, I got fed up with it and installed Linux with a VM and now everything works like a dream. EDIT TO ADD: I would love to do a project like Learn Clojure the Hard Way, but I'm simply not confident in my abilities to do it correctly. I've written some pretty significant programs in Clojure (see my profile), but I wouldn't be able to solve but a few Project Eulers with it. I'm simply too new at programming in general.
  - DigitalJack 14y ago
    I'm a Mac person myself, but use windows for work and have leiningen and clojure running fine. I just used the batch file from the leiningen github to get up and running on windows. Someone else brought up the point that lein needs wget or curl, and that isn't something that is installed by default on windows. I happened to already have them, so I never thought much about it. GNU has a version of wget and maybe curl too for win32. And there is always cygwin if you like. https://github.com/technomancy/leiningen https://github.com/technomancy/leiningen http://gnuwin32.sourceforge.net/packages/wget.htm http://gnuwin32.sourceforge.net/packages/wget.htm

paddyoloughlin 14y ago

I'm interested in learning LISP. How good a choice is learning Clojure as a way of achieving this? I've read a page[1] listing differences between Clojure and other LISPs, but I'm not sure that I fully understand the implications of these differences. [1] http://clojure.org/lisps http://clojure.org/lisps

jrheard 14y ago
Clojure's a great lisp. I recommend it highly. I haven't spent much time with Scheme, but I can definitely say that I greatly prefer Clojure to Common Lisp.

jumanjisama 14y ago

http://youtu.be/VVd4ow-ZcX0 http://youtu.be/VVd4ow-ZcX0 this video by Chas Emerick (co-author of clojure programming) also gives a good introduction to start with clojure, especially for people who uses eclipse.