Anyone knowwhere I can find examples of create-table-ddl useage? https://clojure.github.io/java.jdbc/#clojure.java.jdbc/create-table-ddl Googling around, I get all forms of java examples, but not clojure examples.

Is there a library (Clojure or otherwise) that could be used to alter an existing PDF? For instance put a signature on it, dates etc. I already have experience with clj-pdf (https://github.com/yogthos/clj-pdf), but I'm pretty sure that it (and iText, which it depends on) is only for generating pdfs from scratch.

I know how to write a buffered iamg (name ans) out to a file as png via

(ImageIO/write ans "png" ( "output/test.png"))

ByteArrayOutputStream

and only C would call it a string

@noisesmith : right, it's not a string, it's a ByteArray

I mean, it's trivial to get a string from the ByteArray, but that probably won't do anything at all useful

I need to insert it into an array

byte-array is probably better format anyway

write it to a ByteArrayOutputStream and then copy the bytes over? maybe there's a way to get it to write to the array...

wait, do you have an array already and want to put the image in there too, or do you mean you just need an array? for the latter, there's a method on ByteArrayOutputStream to get its contents as an array

wait

so here is my situatation, I have a postgres1qp db, I'm using clojure.java.jdbc

I need to insert triplests of the form (font-name :: string, unicode :: int, image :: 32x32 png file)

OK - so I would hope it would accept a bytearray for the third arg...

but I don't know jdbc enough to know that for sure

but what I would try, is telling ImagIO to write to the ByteArrayOutputStream then get its byte array and pass it to jdbc - that seems intuitive (sorry to say I haven't tried so I can make no promises...)

another option is to derive a ByteArrayInputStream from the ByteArrayOutputStream (this is an input that gives you the bytes the imagio wrote) and try passing that as the last arg

this document makes it look like jdbc expects an inputstream (if it works with a File object, that's your ticket), so what you want is to make a ByteArrayInputStream out of the ByteArrayOutputStream's array

err - document https://jdbc.postgresql.org/documentation/80/binary-data.html

@qqq

+user=> (import ( ByteArrayInputStream ByteArrayOutputStream))
java.io.ByteArrayOutputStream
+user=> (def b (ByteArrayOutputStream.))
#'user/b
+user=> (.write b (.getBytes "hello, world"))
nil
+user=> (def b-in (ByteArrayInputStream. (.toByteArray b)))
#'user/b-in
+user=> (slurp b-in)
"hello, world"

using a string because that's easier to demonstrate in a repl, but the concept is sound

@noisesmith :

(let [f   (first (filter #(.canDisplay % \a) all-fonts))
      ans (draw-text f "yg" 4 22)
      ba  (ByteArrayOutputStream.)] 
  (ImageIO/write ans "png" ba)
  (j/with-db-connection [conn db-spec]
    (j/insert-multi!
     conn :letters
     [{:unicode 20 :font_name "foo" :png (.toByteArray  ba)}])))

awesome!

Lets say I have a function which has some data as its params and then inside that function I have an anonymous function (with a specific signature (not defined by me)) that closes over that first functions params. Lets say I want to make the anon function a real named function. In javascript, I would have to make a function that returns a function that closes over the param. In clojure I am betting there is a macro that lets me say "call this defined function, and close over this variable" Perhaps the best way to do it is partial so that way I can turn the anon function into a named function that takes one extra param at the begining of its list and then use partial to "close over" the variable I want.

I guess, I solved my own problem. I didn't know to use partial until I started writing.

@slightlycyborg: Also you don't have to have a partial function - you can instead have a defn that returns a fn. This 'inner' function is not usually given a name.

Calling all Singaporean clojurians or anyone who might be traveling to this part of the world, we have a dedicated clojurians slack channel #clojure-sg, please join to this channel if wants to share or wondering what we do over Singapore Clojure.

Hi Everyone! I am following a book on web development with clojure and Stumbled on this bit of code:

(ns 
  (:require [compojure.core :refer [GET defroutes]]
            [clojure.tools.loging :as log]
            [immutant.web.async :as async]
            [cognitect.transit :as transit]
            [bouncer.core :as b]
            [bouncer.validators :as v]
            [guestbook.db.core :as db]))

(defonce channels (atom #{}))

(defn connect! [channel]
  (log/info "channel open")
  (swap! channels conj channel))

(defn disconnect! [channel {:keys [code reason]}]
  (log/info "close code:" code "reason:" reason)
  (swap! channels clojure.set/difference #{channel}))

(defn ws-handler [request]
  (async/as-channel
   request
   {:on-open connect!
    :on-close disconnect!}))

For me it feels like the channels atom is used in a very OOP like fashion. Beeing global in the namespace and changed in the connect! and disconnect! functions

is there a better way to handle this?

I’m an absolute beginner so please consider I know nothing:)

@nadejde you're absolutely right. This is probably to keep the example small. If you're looking to manage state in your application you might want to check out https://github.com/stuartsierra/component

alternatives are https://github.com/tolitius/mount and https://github.com/weavejester/integrant

i have two projects, so I have:

foo/build.boot
foo/src
bar/build.boot
bar/src

oh, I also need this to play nicely with boot.watch, so when I update src/shared, I need foo and bar to both recompile

Hi I am from Java background having 4 yrs experience. I am planning to learn Clojure & ClojureScript. I do not have any knowledge on functional programming 1. How easy or difficult it is learn and create competency. 2. How long would it take to learn for our JAVA resources 3. Where is this predominantly used

1. most importantly it's fun, especially for a java programmer; 2. depends; 3. many of the areas where Java is used

I'm actually using clj/cljs primarily as a js replacement

1. is also dependent alot on motivation / agressiveness

@stijn thank you!

@nadejde that code is pretty idiomatic. reference types are usually stored at the top level of a namespace so other functions in that namespace have direct access. You can choose to fully purify those functions, by passing in the channels atom and having them work on the passed in ref, but that may or may not be the best idea. Depends on the purpose of the namespace and how it relates to the other namespaces in your application and the outside world. But with regard to state management for your whole app, I agree with stijn. A component sort of lifecycle management system for your state is smart.

@ramamurthi_k 1. What d'you mean with easy? Check https://www.youtube.com/watch?v=cidchWg74Y4 and https://www.infoq.com/presentations/Simple-Made-Easy . These talks will give you an idea of why - it's all about motivation and eagerness to learn new stuff (you know 'Beating the Averages' of Paul Graham?), so it may be 'easier' when you have a good motivation. 2. Are they willingly to learn or not? (if not, well, I wouldn't want them as devs - that's what you mean with 'JAVA resources', right?) 3. Where d'you want it to be used. It's not limited to 'one specific area'. It can do what Java can do, but usually in a simpler way. Where is Java predominantly used 😛?

Certainly check https://www.youtube.com/watch?v=cidchWg74Y4#t=2m16s about easiness to learn etc.

Just to add more subjective context: 1. Clojure is the easiest language out there. 2. Knowing Java makes programming Clojure even easier. 3 Mostly web apps and data manipulation. Not yet much in the embedded, memory constrained platforms, like IOT.

> 1. Clojure is the easiest language out there. I like that one 🙂.

It's true 🙂

some would argue it's simple but not easy 🙂

That's my metric for easy

When things get big, they're still the same

well, it's one of the languages that I picked up pretty fast, but I'm not sure if it's because of the language, or just because having background in different other languages makes you pick up languages faster 🙂

\(ツ)/¯

@john thank you

yup

Any opinions on hugsql vs honeysql vs korma? I'm using hugsql right now, but I'm tempted to switch to honeysql due to its composability features looking nicer than hugsql snippets

Korma has fallen a bit out of favor, I think. Honeysql is definitely more amenable since it's plain old data structures. Can I ask what specific parts of queries you're looking to compose?

@mikeb The example I'm thinking about right now is a WHERE clause where I can dynamically add more ANDs

Korma is an ORM library, while the others seems like SQL helpers for Clojure

Korma for Clojure is more like Doctrine for PHP

@curlyfry Haven't use hugsql, but I've used honeysql a lot, am mostly happy with it and strongly prefer it over korma.

@evo @bpiel Definitely prefer the "helpers" route over ORMs. Thanks for the pointers!

You can always combine two libraries

It depends on the SQL queries that you need - if you need complex queries, you should definitely avoid ORM for these.

When you need to write complex SQL, hugsql/yesql/jeesql approach is better imo, but you can always mix and match

(shameless plug) there’s also specql, if you are using PostgreSQL

Here's a fun topic: failure The kickstarter for Sayid Pro is solidly on track to fail. My hopes for reversing that trend are not high, but I would like to at least come away from this feeling like I've learned something. Over the past few months, even since the launch, I've gotten a lot of positive feedback and direction from many people. If everyone who has expressed interest in purchasing sayid pro were to back the campaign, while success would still be far from guaranteed, things would be going much better. I don't think it's a problem of exposure. The kickstarter page has seen over 1k visitors, with a significant portion watching the video in its entirety. So, my question is: Why hasn't this perceived interest translated into backing? Any thoughts and feedback are appreciated. I'm available through email (see https://github.com/bpiel), twitter @bpiel or you can DM me here. thanks!

@bpiel you might get more feedback on #off-topic

Is there something like reify but with a base instance? I know I can refer to the surrounding local scope, but I don't want to reimplement all the interfaces, but the once I care about.

@branch14 I'm pretty sure reify will fill in any not implemented methods with "throw new NotImplemented..."

I'm new to Clojure and having an odd issue, anyone got a minute? Pretty sure it's an easy one

@marcusf sure, just ask 🙂 or perhaps in #beginners if it's a super simple question.

@tbaldridge Allright. Not sure if it fits in Beginner or not, I'll ask here in case. I'm trying to output the current time. I found this snippet online, which works when I do println

(.format (new java.text.SimpleDateFormat "hh:mm") (java.util.Date.))

(defn currTime[]
	(.format (new java.text.SimpleDateFormat "hh:mm") (java.util.Date.)))

(def awesomebutton (button :text "Sometext"))
(listen awesomebutton :action (fn [e] (println currTime)))

This works

(listen awesomebutton :action (fn [e] (println (.format (new java.text.SimpleDateFormat "hh:mm") (java.util.Date.)))))

i believe that currTime is a function

but you aren't invoking it, just printing the funciton

which is an object

Aha, so it is a #beginners suitable question. lol

(println (currTime))

Yep, that worked

Thanks @dpsutton

@tbaldridge I would like the the result of reify to "behave" like a given base instance, except for the reified interfaces.

@branch14 base instance? So you mean you want to inherit a abstract class?

could proxy be what you want?

https://clojuredocs.org/clojure.core/proxy

it lets you give a class or interface and definitions for methods. if any are missing it uses that from the super class

No, I have an instance, for which I want to reify only some interfaces.

so you're looking for what cljs implements as specify!, which doesn't exist in clojure

I looked at proxy, but I already have an instance, not a class.

Yes, CLJS's specify! might be it. But for CLJ.

yes, you can't do that on the JVM

IC, thanks anyways!

well, you kinda can do that if you can restrict yourself in dealing just with interfaces and not concrete classes

but yeah, it's not in CLJ because that's impossible in the JVM for the general case

clojure is easier than common lisp at any rate! 😛

These two ways of accessing a value in a nested map seem equivalent

(def mymap {:a {:b 1}})
(get-in mymap [:a :b])
(-> mymap :a :b)

which one is the preferred form?

I vote for get-in

@gigasquid plz ignore me if you're busy, but running your cool kaggle-cats-dogs and getting a 'No such var: loss/max-index, compiling:(kaggle_cats_dogs/core.clj:174:43)' after 'lein run to train'... any clues about what might be wrong?

(-> mymap :a :b) is the most performant, I believe.

but I wouldn't say one is preferred, the both have tradeoffs

the get-in one is more flexible and works with other types of keys rather than just keywords

(just as an FYI)

@gigasquid I coudn't find cortex 4.0 and am using 5.0 if that's a possible factor.

get-in also allows for a not-found if you need that. e.g. (get-in mymap [:a :b] "not-found")

I am very new to programming and am currently learning Racket. I have fallen in love with the syntax, or lack there of. So, Clojure feels like the natural next place to go,. Are there any good video series on Clojure?

I am reading Clojure for the Brave and True eight now

there are 8 of em? 😉

For instance, there are a plethora of tutorial video series on Python, I am simply asking for a recommendation for a Coursera course or edX course or YT series .

@whitwulf @arthur has a http://lynda.com series on Clojure https://www.lynda.com/Clojure-tutorials/Up-Running-Clojure/413127-2.html ; there are also tons of various videos on Youtube you can hunt for, though quality may vary

And I'm happy to help here as well.

@gigasquid for what's it's worth, adding [cortex.util :refer [generate-id max-index]] to core.clj fixed the error.

@macrobartfast - I can't dig into it right now - but cortex has been changing really rapidly lately approaching 1.0. Not surprised if my stuff broke. I'll have to revisit sometime

Hi all, does anyone have any experience of using Clojure for this?

https://en.wikipedia.org/wiki/Web_Application_Messaging_Protocol

I've found this: http://cljwamp.us

But the client part (which is what I need) is JavaScript using http://autobahn.ws/js

I've found some Java libraries that I could use, but wondered if there's a better way. I've found a WebSocket client for Clojure (https://github.com/stylefruits/gniazdo-jsr356), but not sure if it's suitable.

@gigasquid all good... I'll submit patches as I can. I got everything working... great tutorial, and thanks!

Hello! I searched clojure lib for workflow managment, like airflow or luigi, with schedule tasks, ui and so on. The only result by me — https://github.com/Factual/drake But it seems kind of unusual. Anyone know any alternatives?

for people determined to use clojure.java.jdbc -- is there a bunch of examples somewhere? all the docs here https://clojure.github.io/java.jdbc/#clojure.java.jdbc/db-query-with-resultset show params, but not examples

@qqq honeysql renders to the vector that you pass in for sql-params, so https://github.com/jkk/honeysql has a lot of examples of what those might look like

@rustam.gilaztdinov Netflix has an amazing tool called Dagobah, but unfortunately they haven't finished opensourcing it. They described it at the Conj a couple years ago: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwji7cveqvXTAhWHESwKHfKvDCIQtwIILDAB&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DV2E1PdboYLk&usg=AFQjCNE_uWfxaHqUVxAWLOhRyb1PM6SGtw

I think it beats the pants off of any other dataset building system.

@ghadi this is sad 😞 but thx!

Unrelated to above. I can't believe we only get any? in clojure 1.9 🙂 Things like checking if a value is contained in a list are so miserable as is without it

@matan any? doesn't do what you think it does. Use some if you want to check for membership in a list, or use a set and use set membership operations.

@rustam.gilaztdinov you can view it as sad -- or you can be inspired by how extremely well thought-out it is

the talk is super cool. way nicer than airflow

@ghadi after the some I have to translate to true or false, in order to follow with more logic. that is cumbersome.

unless I play with the language's truthiness rules all along the logic I perform downstream. I don't like the latter option, it obfuscates what the code is doing and is just bizarre

(some #(= % value-i-want) collection) doesn’t seem terrible, right? you get true or false, works for nil

What wiseman said. Or what you said @matan: (boolean (some #{value-you-want} collection)) Take a monetary analogy to the clojure core functions: It's not designed to have an $42.37 bill, but rather a $20, a $1, 10c, some pennies, etc.

most practical cases in clojure you don't have to coerce to true or false, because truthiness in clojure is not insane like other languages

I hear ya

boolean really helps!

for those cases...

that said, i don’t really like the (some #{…} ..) idiom, because of the nil problem.

I am hard to see the gain in alienating most programmers with this idiosyncratic way of handling logic though...

What on earth was the motivation? at the time of language design...

user=> (.indexOf '[a b c d e f g] 'b)
1

Why does transduce calls the transformed reducing function on the final result? https://github.com/clojure/clojure/blob/clojure-1.8.0/src/clj/clojure/core.clj#L6602 reduce doesn’t do that.

it's the "completion" function. A lot of times you want to run reduce then 'fixup' the result at the end. A good example is transient/persistent:

(transduce (map inc) (fn ([c] (persistent! c)) ([c input] (conj! c input))) (transient []) coll)

I know that reducing function looks terrible, so there is a shortcut:

(transduce (map inc) (completing conj! persistent!) (transient []) coll)

But back to the heart of your question, the completing function also "flushes" some stateful transducers

Like partition-all https://github.com/clojure/clojure/blob/clojure-1.8.0/src/clj/clojure/core.clj#L6965-L6971

if a project has a dependency on a particular library that (for whatever reason I haven’t quite figured out) is incompatible with clojure.spec.alpha/1.9, is there anything one can do to remedy the incompatibility? Or is it left to patching the old lib to be 1.9+ compatible?

For example, I’m writing a proxy server that uses 1.9+, but has a dependency on clj-http .. trying to bring that library into my project fails with a whole series of foo fails spec clojure.core/import ... clojure.core/quotable-import-list ... package-list etc.

Which seems to be pretty clear: a bunch of forms in the library aren’t conforming to the defined specs. (though this seems quite strange .. would import and import-lists change between 1.8 and 1.9?). Or I’m doing the dependency-pull-in process incorrectly and I need a clojure adult to hold my hand.

@lwhorton it’s not that import changed, it’s that import used to accept all kinds of garbage that is no longer silently ignored

ah so that form validation in 1.9 is now conditional on whether spec’s on your classpath?

@lwhorton i got bit by that a couple times when i went to 1.9 — i think patching the lib as you say is the solution

or maybe can be turned off, but i’m not aware of a way

Alrighty thanks ill look into that