Very clever!

On Fri, Jan 10, 2014 at 8:10 PM, Håkan Råberg <hakan.rab...@gmail.com>wrote:

> Another style, using channels for local state, but could been plain old
> iterators, slight golf warning:
>
> (require '[clojure.core.async :refer [to-chan <!!]])
>
> (defn uniquify [s formatter]
>   (let [g (memoize #(to-chan (cons % (map (partial formatter %) (next
> (range))))))]
>     (map (fn f [x] ((some-fn #{x} f) (<!! (g x)))) s)))
>
> (uniquify ["a" "a" "a" "a" "b" "a_2" "a_3" "a_3_1" "a_3_1" "a"] #(str %1
> "_" %2))
> ;=> ["a" "a_1" "a_2" "a_3" "b" "a_2_1" "a_3_1" "a_3_1_1" "a_3_1_2" "a_4"]
>
>
> On Friday, 10 January 2014 14:59:10 UTC, Colin Yates wrote:
>>
>> I have a sequence of file names and I want to make them unique.
>>  (uniquify ["a" "b" "c" "a"]) => ["a" "b" "c" "a_1"])
>>
>> This is what I have come up with, but surely there is a better way?
>>
>> What would you all do?  Feedback welcome (including the word 'muppet' as
>> I am sure I have missed something simple) :)
>>
>> (defn uniquify
>>   "Return a sequence, in the same order as s containing every element
>>   of s. If s (which is presumed to be a string) occurs more than once
>>   then every subsequent occurrence will be made unique.
>>
>>   Items will be updated to include an incrementing numeric count using
>>   the specified formatter function. The formatter function will be
>>   given the name and the number and should return a combination of the
>>   two.
>>
>>   The set of unique s's in the returned sequence will be the count of
>>   s's in s."
>>   ([s] (uniquify s (fn [item duplicates] (str item "_" duplicates))))
>>   ([s formatter]
>>      (let [occurrences (atom {})
>>            register-occurrence (fn [item]
>>                                  (if (get @occurrences item)
>>                                    (swap! (get @occurrences item) inc)
>>                                    (swap! occurrences assoc item (atom
>> 1)))
>>                                  @(get @occurrences item))
>>            process (fn [item]
>>                      (let [duplicates (dec (register-occurrence item))]
>>                        (if (> duplicates 0)
>>                          (formatter item duplicates)
>>                          item)))
>>            unique-s (map process s)]
>>        unique-s)))
>>
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