On Thu, Jan 6, 2011 at 10:49 AM, new2clojure <miguel.arre...@gmail.com> wrote:
> I am trying to store into a map the frequency of each [a-z]+ word in a
> file. When I run this code in the repl the resulting dictionary is
> empty. How should I adapt my code to get this functionality right?.
Other people have offered up alternate solutions that should get you
pointed in the right direction but I wanted to highlight an important
issue which may be tripping you up, depending on your background:
> (def dictionary {})
This defines dictionary as an empty map. dictionary is immutable.
> (defn process-file [file-name]
> (with-open
> [rdr (BufferedReader. (FileReader. file-name))]
> (doseq
> [line (line-seq rdr)]
> (reduce #(assoc %1 %2 (inc (get %1 %2 1))) dictionary (re-seq
> #"[a-z]+" (.toLowerCase line))))))
This does not change dictionary. The (assoc) call returns a new map.
The (reduce) call will ultimately return a new map (the result of
calling assoc several times).
The lack of side-effects / assignment can be quite hard to get your
head around if you're not used to functional programming.
As Ken noted, your (get) call needs to use 0 not one (since you always
(inc) it):
user=> (reduce #(assoc %1 %2 (inc (get %1 %2 1))) {} ["these" "are"
"some" "words" "with" "some" "words" "repeated"])
{"repeated" 2, "with" 2, "words" 3, "some" 3, "are" 2, "these" 2}
With (get %1 %2 0) we get the correct result:
user=> (reduce #(assoc %1 %2 (inc (get %1 %2 0))) {} ["these" "are"
"some" "words" "with" "some" "words" "repeated"])
{"repeated" 1, "with" 1, "words" 2, "some" 2, "are" 1, "these" 1}
--
Sean A Corfield -- (904) 302-SEAN
Railo Technologies, Inc. -- http://getrailo.com/
An Architect's View -- http://corfield.org/
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
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