I've been finding uses for Brandon Bloom's transduce mini-library left and
right lately. There is a class of problems where you want to track some
state as you process a seq, and transduce.lazy/map-state enables you to do
that (https://github.com/brandonbloom/transduce).
Here's my solution using it. It is concise and stateless:
(defn uniqify [coll]
(map-state (fn [elem->times-seen x]
(let [x (if-let [times-seen (elem->times-seen x)]
(str x "_" times-seen)
x)
elem->times-seen' (update-in elem->times-seen [x]
(fnil inc 0))]
[elem->times-seen' x]))
{}
coll))
On Sat, Jan 11, 2014 at 12:32 AM, Mark Engelberg
<[email protected]>wrote:
> Very clever!
>
>
> On Fri, Jan 10, 2014 at 8:10 PM, Håkan Råberg <[email protected]>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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