Hi Roelof,
Just a general advice, for figuring out how small things like these work
and why they don't work I find Lighttable (http://lighttable.com/) an
awesome IDE. This is the best thing available to learn clojure (combined
with a good book or online resource of course) and I would have to have
IDEs with an instant inline REPL for different languages too while learning
these.
However, what I usually did (and still sometimes do) is fire up Lighttable,
open a barebone namespace, insert this function:
(defn add-author [book new-author]
(assoc book (conj :authors new-author)))
and
(add-author little-schemer {:name "Gerald J. Sussman"})
then evaluate both and just see what happens. Most of the times something
failed and then it's easy to take one step back and just evaluate simpler
things like:
(conj :authors {:name "Gerald J. Sussman"})
or whatever the smallest example might be. This helps tremendously in learning
and understanding what works and what doesn't work.
Disclaimer: This post is not here to say: RTFM and stop posting questions, but
it is here to show you a better way learning a language.
So I hope you don't get me wrong and enjoy the funny clojure ride.
Best Regards,
Sven
Am Mittwoch, 29. Oktober 2014 12:01:18 UTC+1 schrieb Roelof Wobben:
>
> Hello,
>
> For a exercise I have to add something to the end of a existing map.
>
> So I thought this would work :
>
> (defn add-author [book new-author]
> (assoc book (conj :authors new-author)))
>
> and call the function with :
>
> (add-author little-schemer {:name "Gerald J. Sussman"})
>
>
> then I see this error message :
>
>
> ClassCastException clojure.lang.Keyword cannot be cast to
> clojure.lang.IPersistentCollection clojure.core/conj (core.clj:83)
>
>
> Roelof
>
>
>
>
>
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