@cfleming: I have an external tool similar to the IntelliJ Todo "applet" -- it collects comments matching a certain regex, and when you click on the comment, it jumps the IDE to the corresponding file/line

Clojure gurus! I'd like to have a short comment to one design decision. I have three various environments which all connect to their data sources a bit differently and also the data processing is a bit different. I need to implement n different functions for data processing. I could do this using multimethods and dispatch based on environmental variable value which I know for each environment (defined in profiles.clj). But I was wondering if this could be implemented more elegantly e.g. using protocols. Any suggestions?

I was reading about protocols in "Joy of Clojure" and "Clojure Applied". I think I have an idea how to do it more elegantly. I create one namespace per one environment/defrecord definition, and inside that defrecord I define the data processing functions for that environment. I'll create a git branch for this and experiment a bit. Clojure is so fun. 🙂

Damn, I love Clojure REPL. And using IntelliJ IDEA with Cursive and its REPL makes experimenting with the code so fluent and fast. I was having major difficulties to figure out how to call function b from function a using the same protocol. Then I experimented it using REPL and figured out how to do it in a couple of minutes just by experimenting.

"You're living in your program invoking your tools, instead of living in your tools invoking your program" - Stuart Halloway.

But... I have one issue I can't figure out how to do and the Clojure books I have doesn't provide an example for that.

And what would that be?

(defprotocol EmailProtocol (lowername [this name]) (email [this host])) (defrecord EmailRecord [ourcompany] EmailProtocol (lowername [this name] (clojure.string/lower-case name)) (email [this contractor] (let [contractorname (lowername this contractor) companyname (lowername this ourcompany)] (str "ext-" contractorname "@" companyname))))

This works well when EmailProtocol and EmailRecord are in the same namespace...

But if I put EmailRecord into another namespace then Clojure complains that it cannot find function lowercase...

(def ourcompany (->EmailRecord "CoolCompany")) (lowername ourcompany "David") => "david" (email ourcompany "David") => "ext-david@coolcompany"

So, if defrecord EmailRecord is defined in another namespace, the Clojure complains that: Unable to resolve symbol: lowername in this context

Please evaluate the following forms in your repl.

(ns pro)
(defprotocol EmailProtocol
 (lowername [this name])
 (email [this host]))
(ns user)
(require '[pro])
(defrecord EmailRecord [ourcompany]
  pro/EmailProtocol
  (lowername [this name] (clojure.string/lower-case name))
  (email [this contractor]
    (let [contractorname (pro/lowername this contractor)
          companyname (pro/lowername this ourcompany)]
      (str "ext-" contractorname "@" companyname))))
(def ourcompany (->EmailRecord "CoolCompany"))
(pro/lowername ourcompany "David")
(pro/email ourcompany "David")

You wanna require and namespace qualify the protocol.

Hope this helps.

Damn, that worked. Why didn't I figure that out. 🙂

Thanks a lot!

I defined the protocol (abstraction) in the namespace pro and depend on (`require`) the abstraction in the implementation, the user namespace.

Anytime!

In fact, the definition of the protocol, the record/type, and the coupling of the protocol and the implementation can be in three different namespaces.

With extend-type

This means you can extend a third party type to a protocol by yet another third party in your namespace.

Ok. Good to know. I'm just learning how to use protocols...

They seem to be very powerful abstraction.

This is Clojure's solution to the expression problem. https://en.wikipedia.org/wiki/Expression_problem

who needs types anyway

everything is a pixel type 😛

(seq my-sorted-map) will always return entries in order?

yes

Hi, how can I append into an atom?

(def tv-state {:tales [{m1} {m2} {m3}]})

I want to (swap! tv-state ??? [:tales] m4)

to get tv-state {:tales [{m1} {m2} {m3} {m4}]}

? did you delete your solution? it worked haha

I wanted to test in a repl 😄

XD i just tried it and it works perfectly

(swap! tv-state update :tales conj m4)

(swap! tv-state update :tiles conj new-post-map)

thanks 😄

no problem!

I took me a mental leap to understand that the first time.

You are calling update on the the value of tv-state

and you are passing conj new-post-map as the arguments to update

i kept putting [:tiles] instead of just :tiles

so many tabs in search of the answer... so thanks 😄

how do I ignore a variable when unifying in core.logic? the usual suspect of _ fails in this case: (== x [_ b])

@sova If you use update-in, you can pass [:tiles] -- just in case you want to go deeper into a nested structure and need multiple levels.