Something along those lines :
(def t { 0 {:title "some" :meetings [ :d1 ]} 2 {:title "some2" :meetings [
:d2 ]}})
user=> (pprint (update-in t [1] (fnil update-in {:title "title" :meetings
[]}) [:meetings] (comp vec concat) [:d1 :d2]int (update-in t [1] (fnil
update-in {:title "title" :meetings []}) [:meetings] (comp vec concat) [:d1
:d2]))
{1 {:title "title", :meetings [:d1 :d2]},
0 {:title "some", :meetings [:d1]},
2 {:title "some2", :meetings [:d2]}}
and in a function:
(def *default-value* {:title "title" :meetings []})
(defn assoc-data
"data is considered a seq of additional meeting objects to insert at the
end of the meetings of key k"
[coll k data]
(update-in coll [k] (fnil update-in *default-value*) [:meetings] (comp vec
concat) data))
Concise again, isn't it ? ;-)
HTH,
--
Laurent
2010/9/15 Michael Ossareh <ossa...@gmail.com>
> Hi Guys,
>
> One of the things that has struck me about clojure, by virtue of being
> a lisp, is the concision of the code - I really find it very
> attractive. However yesterday I found something that I couldn't work
> out how to do in a concise manner. Clearly commenting the code was a
> priority once I got it working, however I'd like to ensure I'm doing
> this correctly.
>
> Much of my functional experience comes from JS and dealing with the
> immutability of our data structures is a very interesting learning
> process.
>
> I have a map (a sorted map) which maps an int to a map. The inner map
> contains a vector of data to which I want to conj elements into.
>
>
> { 0 {:title "some str"
> :meetings [{ ... meeting data ... }
> { ... meeting data ... }
> { ... meeting data ...}]}
>
> 1 {:title "some other str"
> :meetings [{ ... meeting data ... }
> { ... meeting data ... }
> { ... meeting data ...}]}
>
> .....
>
> n {:title "some n str"
> :meetings [{ ... meeting data ... }
> { ... meeting data ... }
> { ... meeting data ...}]}}
>
>
> In JS I'd have a loop which looks somewhat like this (assume the data
> above is called storedData and that newData has the data which I wish
> to insert into storedData);
>
> newData.forEach(function(data) {
>
> var key = .... ;
>
> if (!storedData[key])
> storedData[key] = {title: "title"}, meetings:[]}
>
> storedData[key].meetings.push(data) ;
>
> })
>
> In clj, I've ended up with something along the lines of the following
> (edited from what I have in my code base to match the JS example
> above):
>
> (loop [data (sorted-map)
> collection newData
> meeting (first collection)]
>
> (def key ( .... ))
>
> (if (not (nil? (next collection)
>
> (recur (cond (not (nil? (data key)))
>
> (assoc data key
> (assoc (data key)
> :meetings
> (conj ((data key) :meetings) meeting)))
>
> (true? true)
> (conj data [key {:title "some str" :meetings [meeting]}])))
>
> data))
>
>
> The middle section, with the assoc(es) and conj, just doesn't read as
> nicely as the rest of my clojure. Is this a symptom of my data
> structure or is there a more concise way to conj my data into these
> inner vectors?
>
> Also, as a secondary concern, I read on here a while ago that when you
> find yourself typing "((" it's a sign of an issue - how, given the
> data structure I've to work with, woud you access the title of a value
> if not using that "((" syntax, i.e. ((data key) :title)?
>
> Cheers,
>
> mike
>
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