How might I add a third and final condition, where those candidates
with equal scores AND equal counts are all returned together?
A first try was this:
(defn closest-match
"Searches the haystack vecs for the closest match to the needle vec"
[#^IPersistentVector needle #^IPersistentVector haystack]
(letfn [(matching [candidate]
(reduce + (map #(if (= %1 %2) 1 0) needle candidate)))
(closest [v1 v2]
(cond
(and (= (matching v1) (matching v2))
(= (count v1) (count v2))) [v1 v2]
(or (> (matching v1) (matching v2))
(and (= (matching v1) (matching v2))
(< (count v1) (count v2)))) v1
:else v2))]
(reduce #(closest %1 %2) [] haystack)))
(closest-match [1 2] #{[1 2 \a] [1 2 \b] [2 1]})
[[1 2 \b] [1 2 \a]]
(closest-match [1 2] #{[1 2] [1 2 \a] [1 2 \b] [2 1]})
[1 2]
It looks good at first, but I quickly noticed that I broke the whole
reduction by introducing a pair where we expend only a vec:
(closest-match [1 2] #{[1 2 \a] [1 2 \b] [2 1] [1 2 \c]})
[1 2 \a]
What we should be getting [[1 2 \a] [1 2 \b] [1 2 \c]] since each of
them is equally close to [1 2 3]
On Mon, Dec 28, 2009 at 5:20 PM, Robert Campbell <[email protected]> wrote:
> Thanks ajuc.
>
> I updated the implementation to match your algorithm:
>
> (defn closest-match
> "Searches the haystack vecs for the closest match to the needle vec"
> [#^IPersistentVector needle #^IPersistentVector haystack]
> (letfn [(matching [candidate]
> (reduce + (map #(if (= %1 %2) 1 0) needle candidate)))
> (closest [v1 v2]
> (if (or (> (matching v1) (matching v2))
> (and (= (matching v1) (matching v2))
> (< (count v1) (count v2)))) v1 v2))]
> (reduce #(closest %1 %2) [] haystack)))
>
> It now factors in the second step, taking the shortest candidate.
>
> (closest-match [1 2 3] #{[1 2 3] [9 8 3] [1 2] [1] [1 0 3 4] [1 2 3 4 5]})
>
> now correctly returns [1 2 3] instead of [1 2 3 4 5]
>
>
>
>
> On Mon, Dec 28, 2009 at 4:23 PM, ajuc <[email protected]> wrote:
>> I don't know if I understan correctly the requirements, but this is my
>> try.
>>
>>
>> (def v #{[1 2 3] [9 8 3] [1 2] [1] [1 0 3 4] [1 2 3 4 5]} )
>>
>> (defn matching [p v]
>> (reduce + (map #(if (= %1 %2) 1 0) p v)))
>>
>> (defn better-match [p v1 v2]
>> (if
>> (or
>> (> (matching p v1) (matching p v2))
>> (and
>> (= (matching p v1) (matching p v2)) (< (count v1) (count
>> v2))))
>> v1
>> v2))
>>
>> (reduce #(better-match [1 2 4 4 5] %1 %2) [] v)
>>
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