IMHO, the slowdown comes from allocation:
with
(apply merge-with concat (map (fn [x] {(key-fn x) [x]}) s))
you build a map containing a vector, plus a seq (merge-with calls seq on each
argument) for each item before performing a reduction which calls assoc and
concat.
In seq-to-multimap you o
Thanks Jason.
merge-with seems to be made to support a function like this, I wonder
where is the slowdown coming from? Is apply slow?
I named your version seq-to-multimap2. The timing results are below:
user> (def a (reverse (take 10 (iterate (fn [x] (rand-int 100))
1
#'user
Thanks Christophe,
> Using a default return value, you can rewrite the (if-let...) as (conj
> (amap key ()) item).
A good point, getting clojure and clojure :)
(defn seq-to-multimap
"takes a sequence s of possibly repeating elements
and converts it to a map, where keys are obtained
by app
(defn seq-to-multimap
"takes a sequence s of possibly repeating elements
and converts it to a map, where keys are obtained by applying key-
fn
to elements of s and values are sequence of all elements of s with
the particular key"
[s key-fn]
(apply merge-with concat
(map (fn [x]
Hi,
Am 28.04.2009 um 23:28 schrieb Boris Mizhen:
BTW, I hope I'm not abusing this mailing list by asking questions like
this?
This list and the #clojure channel are the right place to ask
such questions. That said, there is the search facility of google
groups and the log of the channel at ht
Hi Boris,
Boris Mizhen a écrit :
> I am starting to learn clojure. I would appreciate comments on the
> utility function below.
> Coding style, idiomatic Clojure, comment style, efficiency, naming
> conventions, indentations (used slime) ... anything I should
> improve :)
>
> (defn seq-to-multima
Thanks Stuart,
preserving order is a nice touch :)
I also did not realize that conj preserves sequence type ...
BTW, I hope I'm not abusing this mailing list by asking questions like
this?
Boris
On Apr 28, 5:15 pm, Stuart Sierra wrote:
> Hi Boris, welcome to Clojure!
>
> This function looks r
Hi Boris, welcome to Clojure!
This function looks reasonable to me. In your example, you don't need
to write "#(identity %)" -- just "identity" is enough. If you want to
preserve the order of objects in the sequence, you can use a vector
instead of a list.
I would use "contains?" in the condit
Hello all,
I am starting to learn clojure. I would appreciate comments on the
utility function below.
Coding style, idiomatic Clojure, comment style, efficiency, naming
conventions, indentations (used slime) ... anything I should
improve :)
(defn seq-to-multimap [s key-fn]
"takes a sequence s
