(apply (resolve '+) [32 32])

cool thanks

awesome, that filter worked

how come this macro doesn’t work?

(defmacro rev-ord [& args]
  `(let [op# ~(last args)]
     (apply (resolve op#) ~(quote 3) ~(quote 9))))

(rev-ord [12 21] ‘+)

I get

java.lang.IllegalArgumentException: Don't know how to create ISeq from: java.lang.Long
              RT.java:528 clojure.lang.RT.seqFrom
              RT.java:509 clojure.lang.RT.seq
              RT.java:648 clojure.lang.RT.cons
              core.clj:29

Use macroexpand to see what it produces.

You'll see that you have (apply (resolve op) 3 9) and apply expects the last argument to be a sequence

ohh cool

thank you

hmm

I wonder why it returns nil...

@trancehime: are we supposed to guess what is returning nil?

ayy

(into [] (map (fn [sched] (get sched "schedule_id")) schedulelist)) where schedulelist is a vector of maps {:schedule_id id}

It's been stumping me for a bit

I wonder if the get is allright. IM used to write (get amount :amount )

@trancehime: schould it not be ( get schedule_id :sched)

well my keys are written as "key" and not :key since they are JSON.

oke have you tried then `(get "schedule_id" sched) I think you have to order wrong in your get

its (get map key) as args

so I didn't have the wrong order

oke, then I do not have a clue, sorry

it is alright, thanks anyway

That whole thing is producing nil? Seems odd since even if map produces an empty sequence you'd get [] not nil

well it doesn't seem to be showing anything, I have the whole thing wrapped into (str )

And your vector of maps is a vector of {"scheduled_id" id} not keywords, right?

Hmm

I just need to verify something first

@seancorfield: ok, yeah, it's producing []

[]

and yeah it's a vector of {"schedule_id" id}

So schedulelist is empty then?

Since map over schedulelist must produce a sequence with the same number of elements.

no it's not, that's the thing

My schedulelist looks like this: [{"schedule_id" 52778}]

Then map must produce a list of one element of some sort.

So why is my resulting vector empty, wow much confuse

I must be doing something wrong

I just want to get the 52778 into a vector without any of the map structure ;(

if you do use only the get it produces a good output ?

If I have this sort of problems I try to make the code first smaller to see what each part produces

good idea

Uncaught TypeError: Cannot read property 'cljs$core$IFn$_invoke$arity$1' of null well that explains a lot

oh I forgot #

ayyy it worked

thanks @roelof for suggest that, now I have fixed the problem

Ah, so what you posted wasn't the actual code?

It was my first attempt at it then I decided to just do (map #(get % "schedule_id") schedulelist) instead

apparently that worked

happy for you it worked @trancehime

Yay! Working code!

Yeah, you can get some really bizarre errors if you omit #.

Working code is good!

all the time working code is great

How canI desctruct this the best `[ { :account bank :withdraw 200} {:account cash :deposit 200} ]' so account1 has the value bank. amount the withdraw amount , account2 cash and amount2 the deposit value

its now 2 things but it can also be three or more later

You can't give things arbitrary names like that. What's the problem you're really trying to solve?

I have a app where I can keep track of my wallet

but now I can only withdraw and deposit money

what I try to do is that I can withdraw money from my bank and deposit it into my cash

According to noonian I could be done with refs and dosync

I try to mimick this with accounts do

`cash 100

to bank 100`

@seancorfield: is the picture clear ?

Not really. Not sure what restructuring has to do with it. And it's way past bedtime here anyway.

good night

it might be easier to work with atoms

I can also try this with atoms

I'm not saying it will be easier, but it could be. I'm not fully familiar with refs though.

not a problem, I have a little project that I use to play with some things

In the future this project would be a real project

I am doing the 4 clojure stuff. shouldn't this be true? (= '(1 4 7 10 13) (take 5 (iterate #(+ 3 %) 1)))

my repl says its true...maybe an older version on 4clojure?

Totally my bad...I pasted the whole expression

what is wrong here (reduce (fn[acc it] (+ acc (get transactions :withdraw) )) (filter #(contains? % :withdraw) transactions)) What I try to do is to sum all the values of :withdraw in for example this vector [ { :account cash :withdraw 100} { :account cash :withdraw 200} ]

but I see this error in repl : Map literal must contain an even number of forms

oke found it

I make a mistake on calling the function

but I see another problem :

I have now this : (reduce (fn[acc it] (+ acc (get transactions :withdraw) )) (filter #(contains? % :withdraw) transactions))) when I call it with (process-user-action [ {:account bank :withdraw 200} ] ) I was expecting to see 200 but I see this as output : `=> {:account #object[clojure.lang.Atom 0x629fee00 {:status :ready, :val {:amount 0}}], :withdraw 200}'

How can I make it work so I can see 200 which is the total of the amounts

roelof: is transactions an atom?

no, its a vector

see the process-user-action call

oh, the value for :account as an atom, right?

yes, account is a atom : (def bank (atom {:amount 0}))

(reduce + (map :withdraw [ { :account :cash :withdraw 100} { :account :cash :withdraw 200} ]))

gives 300 for me

wierd, this code : https://www.refheap.com/112333 does not provide the wrong function

I think the problem is somewhere in the get part

when I do only (get transactions :withdraw) I see this output : nil

and accounts looks like this : [{:account #object[clojure.lang.Atom 0x7225704a {:status :ready, :val {:amount 0}}], :withdraw 200}]

what is transcations, the vector?

that is the transactions that need to be handled

oke, now with this code : (map (fn[transactions] (get transactions :withdraw)) transactions ) ) I see this answer (200) so almost good

clojure is driving me grazy now

giving up for today

this has already costs me the whole morning and a big piece of my afternoon

yeah i think it is becaus

you are passing a vector of transactions into your process-user-action

it just so happened that your vector only had 1 action

that why you had to use map

It thus returned (200) which lazyseq containing only 200

Aside from Luminus is there any other considerable effort in creating a standard way of doing web development?

Never know that I would be so difficult to get the total amount of for example all the items which has :withdraw in it

@grounded_sage: as far as I know not

@grounded_sage: I haven't seen any that's currently maintained aside from Luminus. I'd guess most people who don't use Luminus work things out on their own (I'm doing my web apps from scratch)

@roelof: yeah, I had similar stuff to figure out when doing my app

@trancehime: any tip then how I can do it a better way

Hmm, do what a better way? The whole thing, or a specific part of your task?

The part if I have this '[ {:account cash :withdraw 200} {:account bank :withdraw 100} I see 300

or a better way to use for transactions parameter

OK, so basically

It's a shame. I get that composing libraries together yourself is a lot more powerful. However for people that are looking to get up and running and building stuff for people to make money it's quite daunting having to figure it all out yourself. I'm currently weighing up learning Elixir and the Phoenix Framework vs using Clojure. I much prefer the Clojure language but there is a huge benefit with people all rallying behind a standard way of doing things.

Your entire transaction looks like this: [ {:account cash :withdraw 200} {:account bank :withdraw 100} ] right?

You want to return 300 which is the sum of all values in the :withdraw key as you are withdrawing from two accounts, cash and bank

that can be a example

yes, so I can check if the transaction is valid I need the total of withdraw

and later on the same for deposit

these totals needs to be the same

Do you want one function to accept either :withdraw or :deposit?

so the above example is not valid

or would you make separate ones for withdraw and deposite

@trancehime: both are fine

you only have to make one of the two

Okay

For simplicity's sake, let's just do one of them

Im just curious where I did take the wrong way

First of all, you are on the right track that you should probably pass in maps of the same structure.

It's implied if you are withdraw with cash and bank account, you are taking from the bank

Now you wanted to check for value equality, right?

correct , so if someone takes 100 euro from the bank and puts 80 in cash there wll be a error

all the amounts of withdraw must be the same as all the amounts of deposit

Right

Then can we both assume the vector will only have 2 maps in it.

[{:account your-account :withdraw value} {:account bank :withdraw value}]

for now yes

later on it could be more

if I want to include things like taxes

Hmm, let's think about that for a moment. In a use case where you have to include taxes or interest, how would you model that in the transaction.

This is important because it'll affect how we process the transaction parameter

(For example do we want [[] []])

(Or do we want a massive [{} {} {} {}])

[ {:account cash :deposit 100} {:account taxes :withdraw 20} {:account sales : withdraw 80} ] as a example

I use now accounts I do not have so just a example of a sales with taxes

Okay, good, so we clear up it's just a single vector containing all the stuff.

I could change the transaction if there is a better alternative

im just trying some ideas

Now you mentioned for it to be valid, the :deposit 100 should be equal to the withdraw, right?

yes, so for my sales example 100 = 20 + 80

I made a typo in it , sorry

I will edit it

OK

we are definitely getting somewhere now

Here's what I would suggest - your transaction should be modeled like this:

Assuming your use case is withdrawing some money to put into your :account cash

You should have {:account cash :deposit value} separate from your vector containing your :withdraw maps

That way, you can run map on your vector to sum up your :withdraw values and compare that directly to the value of (get {:account cash :deposit value} :deposit)

If the values are equal, then good, it's valid. Otherwise, do something else to inform the user that it's invalid

oke, so for one transaction make two seperate vectors

a vector [ {:account bank : withdraw 100} ] and a vector [{:account cash :deposit 100}]

Do I understand you right ?

Yeah, we can roll with that

there might be a case where you withdraw from just the bank but deposit into 2 different accounts

yep, that can be

You'd still have to check that the sum of :deposit is equal to :withdraw

So it works both ways

you can use reduce to help you sum up the values, I think.

and I can find the total with ' (reduce (fn[acc it] (+ acc it)) withdraw )'

it will have to be (get {:account cash :deposit value} :deposit)

I will try it that way

I hope this one will work

I'm gonna grab a cookie and come back in case you need someone to ask again

this "simple" things costs me a lot of hours but I still learn a lot

Oh yeah, no kidding, I'm new to CLJ+CLJS too lol

chips when I try this ` (reduce (fn[acc] (+ acc (get {:account bank :deposit value} :withdraw))) transactions ))'

value is unknown 😞

your fn should accept 2 arguments

oke, so I have to think what the second argument is

usually, your function's arguments are the collection you're passing and each item in the collection

Note: (reduce + [1 2 3]) should return 6

I know but each item is known if we have used the get function

that is what bugging me the whole day 😞

maybe use a let here so value is (get {:account cash :deposit value} :deposit)`

what about this: (reduce + (into [] (map #(get % :deposit) transactions)))

that looks to work

It's not very elegant but it's quarter to 10 PM right now so haha

and it works even with 2 maps

oke, it's here 14:45 in the afternoon

here = the Netherlands

just change :deposit to :withdraw if you have to

I noticed

now time to find out how this works instead of my old code

How this works? 😮

yes, why the code with into works and the rest is not working

ah

Nice part I think because IM also learning

(map #(get % :deposit) transactions) is the same as (map (fn [transaction] (get transaction :deposit)) transactions)

I think I have a idea , The into takes care that all the amounts are in a map so reduce could handle it

this gives you a sequence of all :deposit values

wrapping (into [] ...) simply just puts the values of the sequence into a vector

the vector of all the values is then run into a simple (reduce + ...) which should give you the sum of all :deposit values

yep, I figuyred it out by watching and looking in my head what really happens

into is a very handy function if you want to change what type of collection something is

thanks for the help and thinking with me

No problem

I still have a lot to learn

especially thinking in smaller parts , I still want to do too much in one time

I initially started developing everything in Clojure before moving to CLJ+CLJS/Reagent

It helped me a lot to pick up the basics and refreshing myself on FP

I still do everything in clojure . CLJ/CLJS/Reagent is a step to far right no

First learn to master clojure

Time's not really on my side, since it's part of a work assignment I received since November

For me it is . Programming is a hobby of mine

so no dead-lines except I make one

again thanks. IM leaving for a moment. Have to do some shopping. Busy weekend ahead

Right, take care

you too

and I hope your work assignment will bring your further on your profesion

Hehe, thanks I'm sure it will, it's a big thing for me to shoulder on my own

take care and do not forget to relax often

how to make this function smaller `(if (not(zero? ( - (reduce + (into [] (map #(get % :withdraw) withdraw-tranactioons))) (reduce + (into [] (map #(get % :deposit) deposit-tranactions))))))'

if (not(zero? ( - (reduce #(+ (:withdraw %2) %1) 0 w) (reduce #(+ (:deposit %2) %1) 0 d))))

@paszek: thanks

Hi everyone!… how important is to know the Java library ecosystem in order to create real applications in Clojure? I come from a C++ background so I am very unfamiliar with the Java libraries.

it is hard to avoid learning at least something about the core Java API libraries (I/O, collections, strings, dates)

Clojure generally takes the approach that it will embrace the host (JVM) library when it has nothing to add - so that stuff is often invoked directly via Java interop

similarly, there are many useful Java libraries and it is often easiest to interact with them directly

although this depends a lot on the domain

Ok, that sounds reasonable. I guess I should focus on learning Clojure and “jump” to Java land as needed. What do you mean with collections?, Stacks? Queues?

@rcanepa: From my point of view basic web development is fully clojure / clojurescript stuff.

@sveri: Good to know!