On 10/01/14, 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)))
I came up with the following version:
(defn uniquify [words]
(loop [encountered {}
result []
remaining words]
(if (seq remaining)
(let [word (first remaining)
occurences (get encountered word)
modified (if occurences
(str word "_" occurences)
word)]
(recur (update-in encountered [word] (fnil inc 0))
(conj result modified)
(rest remaining)))
result)))
It is a bit Scheme-ish. It builds a map of number of occurences as it
builds a vector, containing the result. It uses the map to figure out
whether to add a suffix or not. It preserves the original order of the
names. The variable names could use some love, but I don't have the
time for it now.
If you want a lazy version, some modification is needed.
--
Stefan Kanev Ś @skanev Ś http://skanev.com/
Giving up on assembly language was the apple in our Garden of Eden: Languages
whose use squanders machine cycles are sinful. The LISP machine now permits
LISP programmers to abandon bra and fig-leaf.
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