:)

what is wrong here : (= "longest" (reduce (fn [a b] (if (< a b) b a)) ["which" "word" "is" "longest"]))

@roelof: if you try to run that in a repl it should give you a reasonably helpful error message.

@roelof: it seems, from some of the issues you have, that you're not using Light Table's major selling point, which is the instarepl - it shows you values and errors inline, which should help with some of the problems you're facing.

oke, I see on instarepl that only the first two words are used

so it seems a parentheses problem somehow

@roelof: idk if you've solved it yet, but your fn parens are wrong. You need another close paren after the if

I did not solved it yet

you can’t compare strings like that

that should be a clue

(< “a” “b”) => ClassCastException java.lang.String cannot be cast to java.lang.Number http://clojure.lang.Numbers.lt (Numbers.java:221)

I did solve it . I needed to use the length of a and b and compare those

what is the meaning of this exercise :

"Multimethods allow more complex dispatching" (= "Bambi eats veggies." (diet {:species "deer" :name "Bambi" :age 1 :eater :herbivore}))

so multimethods are defined with a dispatch-fn

and then different function bodies are invoked depending on the return value of the dispatch-fn

oke

I found out that I need to add something here

(defmulti diet (fn [x] (:eater x))) (defmethod diet :herbivore [a] "veggies") (defmethod diet :carnivore [a] "animals") (defmethod diet :default [a] "I don't know what a eats")

but this one is not good

do you know that keywords are functions?

nope, I just begin learning clojure with the clojure koans

ah

ok

so (fn [x] (:eater x))

can just be rewritten as :eater

yes, and later on eater is given by a name like bambi which is a herbivore

well that’s a map, right?

right

ok

so you have your map, m

if you call (:eater m), it’ll return :herbivore

when you call a multimethod, it’ll call the dispatch-fn, and then call the method that matches the result

so it’ll call (:eater m), which’ll return :herbivore, and will then call the version of diet that corresponds to :herbivore

right?

right

and the return value needs to be veggies according to this : Bambi eats veggies."

does it?

or does it need to be “Bambi eats veggies”?

you are right

where bambi is the value of the :name part of the map

right

oke, so I can do this str ( (:name x) "eats veggies"))

yeah!

well, provided you move the parens around

oke, there is one ) to much

str is a function and there is only one way to invoke a function

??

yeah

you just had the str outside the parens

oke

typo

yeah

bummer, still not good

no?

still a false

with this code :

(defmulti diet (fn [x] (:eater x))) (defmethod diet :herbivore [a] (str ( (:name x) " " "eats veggies.")))

do you have access to a repl?

yep, I use Light table and use now a instarepl

I have changed x in a but then I see this message : java.lang.ClassCastException: java.lang.String cannot be cast to clojure.lang.IFn

yup

so I have to figure out what a has as value

no

look at your code

think about what (:name x) resolves to

is schould be the name of the animal

right

so when you have ((:name x)…

it’s gonna turn into (“bambi”…), right?

right , except x is unknown in that functioon

I think it suppose to be a

right

but think about the error that was thrown

java.lang.String cannot be cast to clojure.lang.IFn

yes, clojure think that the string is a function

right!

but how to solve that

why would clojure try to use a string as a function?

aha, it's in the (:name x) part : name is not a function

nope

well

kind of

it’s technically not a function

but it’s a keyword, which can work as a function

clojure is sometimes very confusing

yeah

A keyword is a function in the sense that it implements IFn.

i will say clojure’s error messages are not my favorite part of the language

@ian right

????

so that error message

java.lang.String doesn’t implement IFn

oke, the str part str ( (:name part) ....

maybe I use join to join the :name part and the rest of the requested output ?

so try something like (“foo” 1 2 3) in your repl

I see the same error message

right

which suggests that the same kind of thing is happening in your code

right?

right

so it do not use str here

well no

it’s not the call to str

((str +) 1 2 3)

vs, e..g, (str (+ 1 2 3))

the last one gives a answer the last one gives the same error message

right

sorry but I still no see the answer

so your code is still (defmethod diet :herbivore [a] (str ( (:name x) " " "eats veggies."))), right?

found it

this is working : (defmethod diet :herbivore [a] (str (:name a) " " "eats veggies"))

great!

still not sure what all those “s are doing in there

but if it works, it works

I have to put some spaces in it. Otherwise I see bambieats instead of bambi eats

but why not “ eats veggies.”

as opposed to ” “ “eats veggies.”

also a possibility

I now see what I did wrong , too much parentenses

easy mistake to make

thanks