On 14 Jun 2010, at 01:14, Todd wrote:
> I'm attempting to write a simple histogram function:
>
> <code>
> (defn create-histogram [f]
> (let
> [words (read-lines f)
> histo {}]
> (doall
> (map
> (fn [w] (assoc histo w (+1 (get histo w 0))))
> words))
> histo))
>
> (create-histogram "./testwords")
> </code>
>
> The input, 'f', is expected to be a file of words, as you'd get from
> '/usr/share/dict/words'.
>
> I don't see how to accumulate the results in the map, 'histo'. This is really
> a question of how does one map a function to a collection and accumulate the
> results...
"reduce" is the canonical way to combine a number of input values into a single
result. Here you're constructing a histogram from a sequence of words, so try
something like the following:
(defn create-histogram [f]
(reduce (fn [hist word]
(merge-with + hist {word 1}))
{}
(read-lines f)))
-Steve
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