Hi. I am running through some beginner guides and I noticed that even if I create the -main function like this

(defn -main
  []
  (println "hello"))

java -cp classes:clojure-1.8.0.jar zero_project/first_file 0

no

technically it is always passed an argument though

and that wouldn't work anyway

java needs to be passed a class name

zero_project/first_file is not a valid class name

The above calls my program though...is something wrong still?

For example, I call it and it returns hello to the console

generally -main takes an arg like [& args] is the moral equivalent of c's argc and argv

it doesn't

you think it does, but something else is happening

if you change "hello" for "hello world" what happens?

wow

def' something else happening

it still prints hello

hmmm so what is wrong with the above syntax?

that command wouldn't run

'java' would complain about the misnamed classfile you are passing it

so I have a directory structure like this:

classes/
    zero_project/
        first_file_init.class
        // other class files

which is why I wrote it like this classes:clojure-1.8.0.jar thinking it start in that directory

lol, was gunna say that may have happened

@hl2zip are you using leiningen?

Yes, I was trying to understand at a lower level what it would look like without lein

oh ok cool, there's a tutorial just for that

I am following this one http://www.flyingmachinestudios.com/programming/how-clojure-babies-are-made-lein-run/

haha ok that's what I was looking for

so the reason the text didn't change, almost definitely, is because you didn't recompile the class from the clojure code

wait, do you always have to run load and then compile?

good question, I don't know off the top of my head. the documentation for compile doesn't really say

no

and you shouldn't run both

compile implies load

and you never have to run compile

if you really want to start bare bones, start with a repl and copy and paste forms in, or pass a whole file as a script to the clojure jar

don't touch compile

so how would I build my .clj file without compile?

(I am assuming the guide I was reading is more or less on the right path)

if you are looking at some sort of beginners guide and it is using compile, drop it, it is junk

http://www.flyingmachinestudios.com/programming/how-clojure-babies-are-made-lein-run/

Its the above

wrong

the load then compile call

and this isn't a beginner's guide

ignore, and forget anything you read there 🙂

java -jar clojure.jar will launch a repl

copy and paste code in to the repl

it isn't a very full featured repl, so you might want to pair it with rlwrap

or use a more full featured repl from a tool like lein, or boot, or something built in to your editor

but that is the way to start

fair enough. Out of curiosity - how do I build manually without lein

it depends what you are doing

I wouldn't build at all

you don't need to

that blog post is conflating "building" with aot compilation

which is what "compile" does

which is not required at all, and generally will make your life more difficult for yourself if you do it all the time, and is only useful in some specific situations which you are unlikely to encounter for some time

java -cp clojure.jar clojure.main my-file.clj

will run your clojure file

if you have a bunch of clojure namespaces

jar them up, then java -cp clojure.jar:my-jar clojure.main -m my-main-namespace.core/-main will run it

clojure code is always compiled to jvm bytecode before it is run

compile and just loading the clojure file are no different in that regard

sorry, what is the command for jarring up the files?

And thank you!

https://github.com/hiredman/clojure-site/blob/df56aef005d5d867213a51c2d3bbec5a86b0acad/content/guides/running_a_clojure_program.adoc

this clears everything up

jar

but just use lein

lein is great

my first clojure project that required a "build" step used makefiles

my first clojure job used maven multi module build when I started

(this was all before lein was written)

if you want a clojure build tool that's a bit more explicit about what's happening then there's boot (I have not use boot)

my current job is using boot, and it is fine, but I am particularly impressed enough to move away from lein for my personal stuff

haha that was my next question - boot

err, not

Thanks, all!

To piggyback on @hl2zip 's earlier question about build tools: I ran into this cool-looking library today called 'System' while trying to bootstrap a Sente server https://github.com/danielsz/system

Has anyone used this? Is it a nice way to bootstrap a new project?

I haven't quite wrapped my head around how to use it, but it seems possibly like a solution to the problem I've been having with static project.clj dependencies -- namely that it's hard to swap dependencies in/out

If I have a list of keys defining a sort order, how can I sort a map (into a list of pairs) according to the order in the list?

Should I just map over the order list and pick values from the map, or is there a nicer way?

Is this a good way to organize a small project of 2 pages : http://clojure-doc.org/articles/tutorials/basic_web_development.html

@grav ok, I guess it’s just (map #(get m %) order)

@kzeidler Let me know how it goes 🙂 Have you seen this example for sente: https://github.com/danielsz/system-websockets

@danielsz Oh goodness, I feel almost starstruck. 🙂

@danielsz: Is there a comprehensive guide to setting up a dev environment with System? I've checked out the individual examples and I'm having a bit of trouble figuring out how to use them to get the "runtime loading of clj dependencies" idea up and running

hi, is there a leiningen template for nrepl middlewares?

@kzeidler If you want to load clj dependencies at runtime, you have a facility in Boot that allows to do that (via pomegranate).

@kzeidler I'm not aware of a guide, I think people learn with the examples. A guide will be welcome, of course.

@danielsz: Gotcha. So Boot + Pomegranate for loading of actual dependency files at runtime, but System can (if I'm reading the docs correctly) initialize and bind those dependencies to the project on demand? (Correct me if I have the wrong idea, I'm comparing a few different libs right now and trying to keep them sorted in my head)

@kzeidler No, System will reload your code, not third-party libraries.

@kzeidler System is a component system + a live coding environment.

@kzeidler System doesn't have semantics of its own. To understand it means to understand Component and Boot.

@kzeidler And both have good guides and READMEs.

@achesnais A little late, but recently I’ve been creating PDFs using https://github.com/whamtet/cljs-pdfkit. I created a simple version of http://cljs-pdfkit.herokuapp.com/ which allows me to develop PDFs using Figwheel

It’s really nice

that's awesome

I really needed this 2 months ago 😉

but i managed

will try this out soon for something else i need to do

no one who can help me ?

Hi everyone! ... Does anyone knows why select-keys returns an unsorted-map when the vector of keys is big (big in comparison with the map) ?

@rcanepa if you look at m it will be unordered in the same way as your last one. maps are not ordered in clojure, it just so happens that for performance reasons, small maps maintain insertion order but that's not something you should rely on

You are so right ! ... thanks @bronsa !

i have a (deftest ...) which calls a function, which i want to debug. but println statements are not showing. what is the best way to go about this? I just call (run-tests.. ) from the repl

@roelofw: it seems like a good starting place :)

thanks , @clojuregeek

I have this code :

(ns paintings.views
  (require paintings.api-get :as api)

  (defn homepage)
  (api/do-both-in-parallel (api/read-numbers))

  )  

but when I want to run it , I see this error message : Exception in thread "main" java.lang.IllegalArgumentException: First argument to defn must be a symbol, compiling:(paintings/views.clj:1:1) What is wrong with my view file

your defn form is malformed

and these cant go inside a ns form

and i think you want the (:require [dep :as alias]) form

@dpsutton this better :

(ns paintings.views
  (:require [paintings.api-get :as api]))

(def homepage
  "makes the homepage"
  []
 (api/do-both-in-parallel (api/read-numbers)))
 

defn

look up differences in def and defn

if so, then I have to find out why both api calls cannot be found

@dpsutton changed, and im diving into the docs to find the differences

it seems that (defn name doc-string? attr-map? [params*] prepost-map? body) is the same as (def name (fn [params* ] exprs*))

and yours is neither

so with def you do not use a docstring

oke, changed it to :

(ns paintings.views
  (:require [paintings.api-get :as api]))

(defn homepage
  "makes the homepage"
  []
 (api/do-both-in-parallel (api/read-numbers))) 

still both api calls cannot be resolved in cursive

oke, after a invalided caches it seems to work

I have this into my handler.clj : (GET "/" [] views/homepage)

so homepage does not have arguments

it does, it gets the request by default

now I see this error from ring : ' Wrong number of args (1) passed to: views/homepage '

aha, that is the 1 argument

so I must change it to [req] ? @mpenet

(defn homepage [request] ....)

thanks

time to choose a template engine I think and look if I can print something on the screen

at this moment, I want to display the json request that it processed by do-both-in-parallel on the browser

I doubt between selmer and hiccup. what is a better one when dealing with a big html template ?

How can I make it work that this function is executed and the outcome is displayed with selmer :

(api/do-both-in-parallel (api/read-numbers))  

I try it with (render ( api ..... )) but that does not work , I see then a argument error

Selmer's render expects a template (string or file) and a map of data.

(off the top of my head -- I'd have to check how we use it... but we use Selmer to create millions of HTML emails every day)

oke, so back to the manual.

I want to display at this moment, only the outcome of that function on my web page

You need an HTML template that has appropriate substitutions in it.

oke, so I cannot display the whole object or do I misunderstood you

web development with clojure is much harder then the 4clojure challenges

Selmer has constructs to display sequences, by looping over HTML fragments.

if you just want proof of concept you can just call (str)on your object

should spit out something and you can make sure that your endpoint is being hit

{% for item in data %} {{item}} {% endfor %}

(selmer/render my-template {:data my-data})

oke, so if I understand you right, the template is the {% ..... } part

Yes, that's in a file that you could slurp in or use Selmer's render-file (from memory, we just use render)

and must the template also be in the views directory

render takes the contents of a template file, not the path to the file.

(yes, hence why we slurp in the file first!)

^^ No caching? 😛

Here's an example from one of our Selmer templates:

<p>Dear {{user.userName}},</p>
	<p>Thank you for posting your photo on {{site.title}}.</p>
	
	{% if not data.accepted-photos|count-is:0 %}
		{% if data.accepted-photos|count-is:1 %}
			<p>The following photo has been approved by our Quality Control Team and is now showing on your profile.</p>
		{% else %}
			<p>The following photos have been approved by our Quality Control Team and are now showing on your profile.</p>
		{% endif %}
		{% for photo in data.accepted-photos %}
			<div>
				<a href="{{data.photo-url}}/{{photo.photo-name}}.{{photo.photo-ext}}{{data.clicker}}"><img src="{{data.photo-url}}/{{photo.photo-name}}_small.{{photo.photo-ext}}"></a>
			</div>
		{% endfor %}
	{% endif %}

@dominicm Yes, we slurp and cache the templates.

@seancorfield ah, you cache yourselves. Selmer has built-in caching. Any reason you don't use render-file?

@roelofw For reference, you should be able to do (selmer/render "{{ data|json }}" {:data {:key :val}}) to get something basic working.

Yes, complex reasons 🙂 We have a cascading algorithm for selecting a template, based on locale and various other considerations.

There are 2 hard problems in computer science...

We have one code base supporting nearly 100 different web sites in over a dozen locales (including RTL languages!).

@dominicm and data is the outcome of the function ?

Yeah.

so I can do (selmer/render "{{ (api/do-both-in-parallel (api/read-numbers)) |json }}" {:data {:key :val}})

No

(selmer/render "{{ data|json|safe }}" {:data (api/do-both-in-parallel (api/read-numbers))})

Thanks, I will try it out. Later I have to make a real template but I have not found a nice one

Selmer is great, once you get used to it 🙂

Wierd, I now see this error : Unable to resolve symbol: ???? in this context, compiling:(paintings/views.clj:6:1)

Django figured out the perfect compromise to templating — Jinja2 perfected what is available and better defaults.

but there are no ??? in the template to be found

@dominicm so I can use ninja2 also als template engine ?

@roelofw My comment was in response to @seancorfield, Jinja2 is a Python library, inspired by the same thing as Django

oke, one of you two know why I see the resolve symbol: ??? with this code :

(ns paintings.views
  (:require [paintings.api_get :as api]))

(use 'selmer.parser)

(defn homepage
  "makes the homepage"
  [req]
  ⁠⁠⁠⁠(render "{{ data|json|safe }}" {:data (api/do-both-in-parallel (api/read-numbers))}))  

(ns paintings.views
 (:require [paintings.api_get :as api]))

file src/paintings/api_get.clj should be required as paintings.api-get

it's the other way around, you can't have dashes in filenames, but you certainly can have underscores as namespace names

both foo.bar-baz and foo.bar_baz will match foo/bar_baz.clj (but only the namespace that's defined in bar_baz.clj will actually load, obviously)

ah, so that's definitely not it then. I figured it might be a misc bug creating some confusion further down.

@roelofw is there more to your stacktrace that you can share? The suggestion seems to be that (defn homepage is the problem

here is a repheap of the whole output : https://www.refheap.com/124075

And what's on line 6 of paintings/views.clj?

(defn homepage

(sounds like you have non-ascii characters in the code -- did you copy'n'paste it from a web page?)

Nope, I typed it myself

can you show us the whole input?

Oh, you have (use 'selmer.parser) which will only make render available at runtime, not compile-time.

That works in the REPL, but not in a Clojure file.

oke, then I misunderstood the readme of selmer

You need to have [selmer.parser :refer :all] in your :require clause in ns instead.

Most readme files show REPL usage.

They assume you'll do the mental mapping to ns when you write code outside the REPL.

oke, the view file looks now like this :

(ns paintings.views
  (:require [paintings.api_get :as api])
  (:require [selmer.parser :refer :all])
  )


(defn homepage
  "makes the homepage"
  [req]
  ⁠⁠⁠⁠(render "{{ data|json|safe }}" {:data (api/do-both-in-parallel (api/read-numbers))})) 
 

is is now good ?

look at a file online to see how to format your ns form

you shouldn't be using two requires

(ns paintings.views
  (:require [paintings.api_get :as api]
            [selmer.parser :refer :all]))

(and having that _ in the namespace is really jarring... in paintings/api_get.clj I'd expect the ns to be paintings.api-get not paintings.api_get)

Rule of thumb: in Clojure, symbol names never contain _, only filenames have _.

oke, I was naming it like that because the file gets data from a external api

any suggestions how I can name it better ?

The file will be api_get.clj but the namespace should be api-get.

Is that now producing the correct result?

is it possible to have interop with a npm Javascript library? for example, if i wanted to write an application that makes use of the nodegit library...

@ezmiller While running in Node, yes. You can just call (def Foo (js/require "foo"))

can you elaborate a bit about what “while running in node” means?

Well, when you run the application in node

interesting. so you’d write a node application that would load up a clojure jar?

is there an example repo somewhere of what that’d look like?

No, you'd write ClojureScript application that is compiled to Node compatible JS

This might be interesting read: http://yogthos.net/posts/2016-11-30-Macchiato.html

@juhoteperi very interesting. thank you. this all because i want to write something that serves files stored in git(hub), using nodegit or js-git. didn’t see anything like this for clojure…

There is JGit for Java: https://eclipse.org/jgit/

For example Boot uses that: https://github.com/boot-clj/boot/blob/master/boot/worker/src/boot/jgit.clj

And there seems to exist a clj wrapper for jgit: https://github.com/clj-jgit/clj-jgit

Oh, promising. Thanks!

i know i've seen some guides for how to contribute to the clojure jira, about formatting patches and other things. does anyone know where i can find that again?

@dpsutton is still fails with the same error : Unable to resolve symbol: ???? in this context, compiling:(paintings/views.clj:5:1)

still haven't seen the input text you are using so don't know how to help

I will try to re type that part ahain

don't type it

copy it

what do you mean with the input text ?

your file paintings/views.clj

just upload the file here

views.clj :

(ns paintings.views
  (:require [paintings.api_get :as api]
            [selmer.parser :refer :all]))

(defn homepage
  "makes the homepage"
  [req]
  ⁠⁠⁠⁠(render "{{ data|json|safe }}" {:data (api/do-both-in-parallel (api/read-numbers))}))   

and still on the (defn homepage line 😞

can you delete the defn and in its place put

done

you just want to see if the endpoint is working

and if there's any weird characters in there get rid of them

That displays the text on the webpage

so its working

awesome

now put this function

Then I see this as message on my webpage : clojure.lang.LazySeq@5435c2de

try (defn homepage [req] (str (doall (api/...)))

yes , that is schowing the whole clojure object so my first step is working

great

Thanks a lot

so now try to put it back in the render stuff

when I do : (defn homepage [req] (render "{{ data|json|safe }}" {:data (api/do-both-in-parallel (api/read-numbers))})) . I see the same output as with doall

thanks a lot

tomorrow I will try to make a template which displays a record instead of a big clojure object

@dpsutton one question: Must I make a directory templates in the src directory or can it be in the same directory as the views code file

@prakhar that's a common problem with the short-hand fn syntax. Your first example is saying "create a vector, then call it"

try this instead: (map #(vector % 0) '(1 2 3 4 5))

ah nice! thanks a lot @tbaldridge. I’m a big fan of your videos! Thank you 😃

hrm....not sure why the second one worked though....

(map (fn [x] [x 0]) '(1 2 3 4 5))

sorry, it should be this

@roelofw Most folks put the templates in the resources folder instead of src. That should be on your class path at runtime too.

oke, I have to find out how to do that , Thanks @seancorfield

@roelofw You can do (slurp ( "path/to/template.html")) and it will read in resources/path/to/template.html.

Leiningen will automatically put resources on your classpath along with src as I recall...

oke, I will try it tomorrow

Im now looking for a nice portfolio layout which can work with different layouts. Some paintings are landscape and some are not

So im thinking about a masonary template

I'm no front end guy and certainly no designer so I'll resist offering advice on that part 🙂

im also not

Im get a better feeling with just making back ends

If it's for artwork, I'd be a bit hesitant about a masonry template. I'm not really a designer, but it seems to me you want something that gives each painting enough room to be appreciated.

So, maybe a simple grid of with some padding in between and then a way to popup an individual painting to get a better view.

@fiddlerwoaroof That can also be but I do not know what format ( landscape or not) the paintings are

I read them from a external api

If you make a bunch of squares and then set their background-image to the image and then set background-size to contain and use margin for padding, it doesn't matter whether the image is portrait or landscape.

oke, for another site I have used this template : http://themes-pixeden.com/landing/urku/portfolio-masonry.html

But, I'm not a designer, so don't listen to me 🙂

Can't it be that there will be space between images when there are 7 landscape and 3 non landscape

O, I listen and try to see what you mean

I guess I was thinking that the extra space may not matter and will, in fact, help showcase the paintings better.

oke, I can always try

@fiddlerwoaroof thanks

@fiddlerwoaroof you mean something like this : http://jeremycowart.com/portfolio/

just watching clojure conj videos (or starting to watch them). I read them basically as "write immutable code". Which sounds perfectly sensible. I have been waiting for that to happen in a way. But we need more than conventions. We need tooling to enforce these conventions. hint: that is still missing

(and I think clojure is especially well suited to tackle this problem)

@nha I think most people agree that tooling needs to catch up. Spec (as Rich mentioned) is the first step. After people start using Spec more it's rather trivial to say "You said function X took foo before and now it requires foo and bar...can't do that, better rename"

@seancorfield when you had it about the resources directory for selmer templates , you mean that one or resources/public ?

Close - not so much 'write immutable code' as 'write migratable specifications'. In fact, he even noted early in the talk that code is by definition not immutable. What matters more is that the guarantees - the specification of what the code requires and provides - should be open for expansion, whether that be requesting less of the user or providing more.

Code can be used to generate immutable artifacts, but if those artifacts share the same 'name', they still ought to maintain a specification that is at least as strong.

Notably, the one benefit I see from his discussion of using temporal labeling for a namespace is that it gives you guarantees for progression - if you move forward in time, you should have a guarantee that future versions of the same namespace are at least a strong as prior versions.

That's probably the ordering mechanism needed in contrast to SHAs. I wonder how that plays with forks? Hmm.

I couldn't help but wonder if he had a certain Javascript ecosystem's left-pad debacle in mind with all this.

@alexmiller is this intentional?

user=> (dosync (alter (ref 0) inc))
1
user=> (dosync (alter (ref 0) (io! inc)))
java.lang.IllegalStateException: I/O in transaction

user=> (swap! (atom 0) inc)
1
user=> (swap! (atom 0) (io! inc))
1

(swap! a f). Note that f may be called multiple times, and thus should be free of side effects.

You're suggesting that swap! should throw too?

not should, but I expected it to, yes

though pure function and tx function - are not exactly the same, yes

Maybe? There are performance ramifications

would have made io! so much more useful

what is the common way to default an array/seq js snippet

// if the coll is nil we are going to default to empty array
coll = coll || [];

(or col []) i guess, but cant most functions that expect a list handle nil (returning an empty list)?

geez, why I didn’t try that ! sorry to bother you guys !

thank you @olslash

sure