beginner q about partition: why does (partition 10 ‘(1 2 3)) return an empty list? I'd think from the docs it would return either ((1 2 3)) or (1 2 3). am I totally off there?

@mss The reason is that you do not have enough elements to make a single partition of that size. partition-all works the way you want.

someone who can help me telling me if im on the right track ?

oh hi guys

can anyone please help me with a korma raw statement

i just can't seem to manage

i looked everywhere and the documentation is just not made for my needs

is there anybody out there ?

@avabinary Usually you should go ahead and ask away. Don't ask to ask. That being said, I have no clue about Korma

:)))

i need to perform an upsert

tried using the

(raw ...)

(insert users (values {:name "bob" :job "clojurian"} (raw "ON DUPLICATE KEY `name`="bob" UPDATE  ...")))

clojure.lang.ArityException: Wrong number of args (2) passed to: core/raw

Not an expert, but I used korma in the past, anf for raw sql I used jdbc/execute!

not sure I want to do that, stepping out of korma prepared statements

on their docs, they say that (raw) will insert strings directly into their api

@avabinary check that you are correctly escaping double quotes in your string

nope

I used

(format ...)

(raw "ON DUPLICATE KEY 'name'="bob" UPDATE ...") should be (raw "ON DUPLICATE KEY 'name'=\"bob\" UPDATE ...") I think

Someone who can give me some hints on exercise 5 here : http://www.braveclojure.com/do-things/#Exercises

I think I have to rewrite this code :

(defn better-symmetrize-body-parts
  "Expects a seq of maps that have a :name and :size"
  [asym-body-parts]
  (reduce (fn [final-body-parts part]
            (into final-body-parts (set [part (matching-part part)])))
          []
          asym-body-parts)) 

to make this work

and use iterate or repeat ?

Am I on the right track ?

@roelofw: the exercise just says to write a similar function that produces 5 of each body part. I'd probably start afresh but use the structure of that function as a guide for my new function.

Then exercise 6 wants you to produce another new function that accepts a number as well as a collection and produces a result with that many of each part.

At least, that's my reading of what you linked to. I haven't read that book nor tried the exercises.

Looking at the code, I'm guessing matching-part is key?

@seancorfield I think so. this is a part of the output of the orginal function :

[{:name "head", :size 3}
      {:name "left-eye", :size 1}
      {:name "right-eye", :size 1}
      {:name "left-ear", :size 1}
      {:name "right-ear", :size 1}
 

@roelofw I too am not familiar with the exercises or the book however I think matching-part is currently returning the right- version of a left handside part e.g. given left-eye returns right-eye which better-symmetrize-body-parts is then adding as a set into the final-body-parts using reduce to accumulate the final body parts collection. Your going to have to create a fn that given a left body part - returns 5 body parts instead i.e. eye-1, eye-2 etc. and use that in a new version of better-symmetrize-body-parts. As with most things there are several ways to do this.

@agile_geek Oke, im thinking of chancing this line (into final-body-parts (set [part (matching-part part)]))) to (into final-body-parts(iterate 5 (set [part (matching-part part)]))))`

I only have to find out how I make the number a parameter of the other function so I get the output the challenge wanted

@roelof try it but I don't think it will give you what you are expecting.

@agile_geek nope, it gives me this error message :

ClassCastException java.lang.Long cannot be cast to clojure.lang.IFn  clojure.core/iterate (core.clj:2904) 

so again back to the drawing board

maybe I better can do chapter 4 and 5 first , Maybe then I get a idea how to solve these 2

@roelofw (iterate f x) returns a lazy sequence of (x, (f x), (f (f x)), ....)

I still have the idea of doing the call to matching parts several times

so you're asking it to call (5 (set [part (matching-part part)])) and 5 is not a function

Oke, that is not what I wanted. I wanted something like this in a imperatieve language ;

for i = 1 to 5 ; matching-part(i)  

i think it might be better to modify matching-part to return what you want, rather than call it for the same result 5 times.

Still think you have a problem - call (matching-part {:name "left-eye" :size 1}) in a repl and see what it returns...then think about calling it many times

^^

exactly what I suggested further up

that one gives this output : (do-things.core/matching-part {:name "left-eye", :size 1})

but when I do it like this :

(def asym-hobbit-body-parts [{:name "left-eye" :size 1}])

(defn matching-part
  [part]
  {:name (clojure.string/replace (:name part) #"^left-" "right-")
   :size (:size part)})

(defn better-symmetrize-body-parts
  "Expects a seq of maps that have a :name and :size"
  [asym-body-parts]
  (reduce (fn [final-body-parts part]
            (into final-body-parts (set [part (matching-part part)])))
          []
          asym-body-parts)) 

I see this output : [{:name "left-eye", :size 1} {:name "right-eye", :size 1}]

maybe I can change something in this line : {:name (clojure.string/replace (:name part) #"^left-" "right-")

and make there some sort of loop

No one who can give a hint how to solve this ?

seems like a few of us have been really responsive

it’s challenging, think about it, draw it out

the prompt specifically says it’s difficult, read ahead and you might learn more and you can revisit it.

maybe I go that way. These exercises have cost me to many time

or maybe FP is not my thing

keep reading, it’s good stuff. just know that it’s supposed to feel this way, no one gets it immediately.

Then time for chapter 4

there we go.

@cschep ??? What do you mean with there we go

haa, sorry I was just being encouraging. like.. hey that’s the spirit! good luck!

you got this.

🙂

oke, I have read all the text very quick and I think I understand it

After dinner I will try to make the exercises of that chapter

and I hope I have more luck then with the exercises of chapter 3

Sorry, another question. I have made the suspects.cvs into the root directory.

and set it with this : (def filename "suspects.csv")

but when I do (slurp filename) I see a file not found error message

found it. it was a typo

It this right. Im confused now. I think I need a break

I have to do this : Turn the result of your glitter filter into a list of names

I did :

(defn only_names
  [records]
  (map :name records)) 

and used it like this :

(only_names(glitter-filter 3 (mapify (parse (slurp filename))))) 

and see this as answer : => ("Edward Cullen" "Jacob Black" "Carlisle Cullen")

and another one

I have this code :

(defn append_name
  [name gitter-index records]
  (into records  {:name name :gitter-index gitter-index})) 

and used it like this : (append_name(mapify (parse (slurp filename))) "Roelof" 2)

and now I see this error message : ClassCastException java.lang.Long cannot be cast to clojure.lang.IPersistentCollection clojure.core/conj--4345 (core.clj:82)

looks like records will be equal to 2 and into's first argument should be a collection

chips. you are right. IM mixing up my parameters

also never heard of mapify

nope, was not explained in this chapter

When I do (append_name "Roelof" 2 (mapify (parse (slurp filename)))) I see this output :

[:gitter-index 2]
 [:name "Roelof"] 

so something is still not right.

Clojure is not easy for a beginner

maybe walk back a bit. what's (mapify (parse (slurp filename))) evaluate to?

I see then this answer : => (fwpd.core/mapify (fwpd.core/parse (clojure.core/slurp fwpd.core/filename)))

sorry, i mean what is it's output?

Sorry, I did it again and saw this output :

mapify (parse (slurp filename)))
=>
({:name "Edward Cullen", :glitter-index 10}
 {:name "Bella Swan", :glitter-index 0}
 {:name "Charlie Swan", :glitter-index 0}
 {:name "Jacob Black", :glitter-index 3}
 {:name "Carlisle Cullen", :glitter-index 6})
 

@jjfine ^^^

yeah, ok. i think i understand what you're trying to do

if you look at into, the second argument is treated as a sequence

look at what happens when you call seq on {:name "Roelf" :gitter-index 2}

so I have to do (seq {:name "Roelf" :gitter-index 2} ) ?

not to get the right answer, but it should help explain why you're getting that result

when I do that I see this as output : ([:name "Roelf"] [:gitter-index 2])

exactly

and that is not what I want

that's why it added those two vectors to the list

so into is not the right function. maybe I have to use conj then

bingo

yes, that is the right one

I see now the right answer

I have a lot to learn . I have the feeling that I do baby - steps now

into and conj aren't the easiest functions to understand at first

I see

time for a break before my head exploses

Many many thanks