I wouldn't say such a thing is impossible, but at least the Clojure reader does not preserve this information. I think it will preserve the starting line and column in the input file of some selected expressions, but not all.

There are other libraries that can read Clojure code and/or EDN data and preserve other things that the Clojure reader does not.

hmm. it looks like i can leverage pprint for formatting. in which case, is it possible to read a def'ed expression as a string?

(defn my-func [] 1)

(fn->str my-func)
=> "(defn my-func [] 1)" 

i'm sure a lot has changed since i was at university, but one common theme of nearly all the languages i remember using was that they were strongly typed, which of course we don't see in Clojure. in my opinion it's worth learning any strongly typed language at a basic level just because they're unavoidable in the real world, and especially at uni. but focusing on Clojure certainly will not "mess you up" for a CS degree, and in fact you might find yourself writing better object oriented code with reduced state because of your exposure to Clojure / LISP.

oh I see so basically what you are saying is that by learning functional lisp programming, I would actually be able to write better OOp code

wow this answer is great thxs

knowing Clojure might also make you the hippest kid in your class 😎

Chris, my first serious programming instruction was done in Scheme in college, and it was wonderful. It expanded my mind and exposed me to new things, and the following semester I was writing linux networking code in C! I also have a friend who learned programming with Lisp in high school, and it was a formative experience for him, too. You are learning cool things and they’re fun! There’s NO downside to that AT ALL. 🙂 I have never ever ever met anyone who ever said “I regret having fun learning a cool unusual programming thing”

@U010GL90FN0 Thxs for your answer! I already thought that lisp is such a cool language, and now I'll just keep going 😄

For what it's worth, I help teach courses in a top-ten CS program, and we teach scheme as well. LISPs are nice when saying things about the mathematical properties of computer programs

Hmm. I heard that a lot. Of how lisp is good for mathematical representation, but I didn't quite get it because, when you write inside parentheses and with prefix notation, it doesn't look like the conventional mathematical notations we usually see. I know notation and the styling isn't rly anything but would it be ok for you explain that a little bit? Thxs @U0120B5AN2W

Sure. The notation doesn't really matter. It's more because of the properties of referential integrity (https://en.wikipedia.org/wiki/Referential_transparency) and because you can prove things about them using mathematical induction.

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

It's hard to prove things about programs where the state varies all of the time.

Oh I see. So basically immutabilty, pure functions, and the things you talked about mathematical induction and referential transparency makes this better clojure better than other languages with mutable data types

That's cool I didn't know that Thxs 😄

are you familiar with deps.edn? if so then you can include ragtime as a dependency and then require it from your code, just as you would with a lein based project.

{:paths ["src/clj" "resources"]
 :deps  {org.clojure/clojure {:mvn/version "1.10.1"}
         ragtime             {:mvn/version "0.8.0"}}}

Just like with Leiningen! You just have to call ragtime.repl/migrate with your configuration. https://github.com/weavejester/ragtime/wiki/Leiningen-Integration

> database configs go into the deps.edn You can load the config on the function that's being invoked, just like the Lein integration example. > Should I write a lib? IIUC, no. You may have to write a ns to invoke it with (e.g.) cli -m my.migration

@U1UQEM078 I am so new to clojure that I am probably tripping on something extremely simple. I am able to apply migrations in REPL:

Clojure 1.10.1
user=> (ns user (:require [ragtime.jdbc :as jdbc]))
nil
user=> (def config {:datastore (jdbc/sql-database {:connection-uri "jdbc:sqlite:resources/db.sqlite"}) :migrations (jdbc/load-resources "migrations")})
#'user/config
user=> (require '[ragtime.repl :as repl])
nil
user=> (repl/migrate config)
Applying 001-foo
nil
user=>

(Side note: if you 3 backticks as a code delimiter, the formatting is preserved)

Yes, that's expected behaviour and essentially what you'll accomplish through the cli invocation

So my qustion is, to achieve zero argument migrate in REPL, where do I place the def statements so that they are automatically sourced?

You can put those statements in a file and invoke them with clj filename

$> echo "(def a 3) (println a)" > example.clj
$> clj example.clj                                                                                                   
3

Oh, ok that makes sense, so when I am to do migrations I just call that. Thank you, not sure why I did not think of it.😂

NP! You can also create "task" namespaces and invoke those normally. clj -m namespace will call whatever is in the ns' -main

$> echo "(ns example2) (def a 3) (defn -main [] (println a))" > src/example2.clj
$> clj -m example2                                                                                                   
3

Hmm, that did not seem to work. It executed the file but did not enter the REPL. There is probably a way to execute a file and enter REPL.

I added a file migrations.clj at the project root.

(ns user (:require [ragtime.jdbc :as jdbc] [ragtime.repl :as repl]))
   
    (def config
      {:datastore
      ¦(jdbc/sql-database {:connection-uri "jdbc:sqlite:resources/db.sqlite"})
       ¦:migrations (jdbc/load-resources "migrations")})

Then tried clj -m user and it gave me the following:

Execution error (FileNotFoundException) at clojure.main/main (main.java:40).
Could not locate user__init.class, user.clj or user.cljc on classpath.

Full report at:
/tmp/clojure-5805258766426369068.edn

The 2 behaviours are expected, let me elaborate

> It executed the file but did not enter the REPL. That's expected. If you want to be in a REPL, you have to start one (with clj or clj -r)

$> clj 
Clojure 1.10.1
user=> (require 'example2)
nil
user=> (example2/-main)
3
nil
user=>

> Could not locate user__init.class, user.clj or user.cljc on classpath. That's also expected, since you've added the file at the project root and the default classpath is /src

Another issue you'll probably run into is that the filename has to match the namespace (due to java constraints). migrations.clj should have (ns migrations)

Hmm, I want to be able to enter REPL and call migrate and rollback

OK, so basically, I am trying to enter REPL with the following requirements and definitions applied:

(ns user (:require [ragtime.jdbc :as jdbc] [ragtime.repl :as repl]))
   
    (def config
      {:datastore
      ¦(jdbc/sql-database {:connection-uri "jdbc:sqlite:resources/db.sqlite"})
       ¦:migrations (jdbc/load-resources "migrations")})

$> clj -e "(require 'example2) (in-ns 'example2)" -r
#object[clojure.lang.Namespace 0x1917d90f "example2"]
example2=> (-main)
3
nil

Or, using the first script file (without a ns)

$> clj -e '(load-file "example.clj")' -r
3
user=> a
3 

For some reason, it does keep the config variable defined, nor are the require statements are honored.

You have a typo on the ns name. migrate -> migration

just chiming in 2 hours later, but i also find it useful to create aliases for tasks in deps,edn which you can run without having to specify file names: clj -A:migrate

@U1UQEM078 wow, that worked, thank you. I am from C++ world, so much new stuff to grasp that I am misspelling :(

@joshkh I have been lookng at the :aliases and tried: :migrate {:main-opt ["-e" \"(require 'migrate) (in-ns 'migrate)\""]}}

So can C style escape sequences be used?

hmm, i don't know. i usually just create a namespace for each alias, and then i can leverage arguments from the command line. for example:

{:aliases {:deploy-to-aws {:main-opts  ["-m" "myproject.deploy"]
                           :extra-deps {com.datomic/ion-dev {:mvn/version "0.9.251"}}}}}

(ns myproject.deploy)

(defn -main [& [lambda-name]]
  (infof "Pushing lambda to AWS: " lambda-name)
  ...)

$ clj -Adeploy-to-aws send-email-lambda

and using that :`extra-deps` key let's you isolate dependencies (such as ragtime) that you don't necessarily want in your core code

@joshkh, that worked!, I just have to figure out how to pass a string in for up and down migrations, but I think I have the information to do it. Just need to put it together. Thank you for helping me through my first day as an aspiring clojerian.

flatten only works on sequential collections (as mentioned in the docstring)

You can have a flatten that works on all collections by substituting sequential? for coll? in the source.

(defn flatten- [x] (filter (complement coll?) (rest (tree-seq coll? seq x))))

#reagent channel will be able to help much faster.

How did you set your repl namespace?

@U11BV7MTK I don’t think I did explicitly? My shadow-cljs.edn looks like this

{:deps   true
 :builds {:app {:target     :browser
                :output-dir "public/out"
                :asset-path "/out"
                :modules    {:main {:init-fn alpha-journal.core/main}}
                :devtools   {:http-root "public"
                             :http-port 8020}}}}

@U11BV7MTK then in Calva I switched namespace to my main file:

cljs.user=> (ns alpha-journal.core)

Your repl prompt shows alpha-journal.core

I’m wondering how you set that

Ah that’s why

You created a new ns

Rather than going into the one defined

Restart your repl and use require and then in-ns

Otherwise you’re defining a new namespace

Gotcha, thanks I’ll try that out now

@U11BV7MTK Thanks! that fixed it. Quick question, is there any particular reason why I have to use the delayed eval quote for my namespace: (in-ns 'alpha-journal.core) vs (in-ns alpha-journal.core) ? Thanks for all the help once again

It’s not delayed eval. If you eval a random symbol it tries to look it up in the environment and errors if it’s not defined

The quote makes sure we are talking about the symbol rather than what that symbol resolves for

Think the symbol ‘+ versus the function “add” which it points to in the environment

Make sense?

So there is no var defined as alpha-journal.core. We’re using the symbol itself

Got it, thanks for the clarification, helps clear up a lot about the use of quote in general 🙂

Definitely!