Hi everyone,
Does anyone know of a straightforward way to get something like
clojure.math/combinatorics/partitions that works more like partition in the
core library, that is, that only selects partitions with adjacent elements?
In other words, right now this is the problem:
(require '[clojure.math.combinatorics :as c])
(c/partitions [:a :b :c] :min 2)
=> (([:a :b] [:c]) ([:a :c] [:b]) ([:a] [:b :c]) ([:a] [:b] [:c]))
But that ([:a :c] [:b]) there in the second position isn't a proper partition
because :a and :c aren't adjacent in the original vector.
I feel like there's got to be a standard, canonical solution for this, or some
existing sequence or combinatorics function with a funny name that just returns
(([a :b] [:c]) ([:a] [:b :c]) ([:a] [:b] [:c])) in this situation. I just
don't know it...
The best I can come up with is kind of a hackish workaround that only works
when the original vector is sorted, namely, flattening all the partitions and
testing to see whether they are sorted too, i.e.:
(require '[clojure.math.combinatorics :as c])
(defn test-fn [part]
(let [f (flatten part)]
(= f (sort f))))
(filter test-fn (c/partitions [:a :b :c] :min 2))
=> (([:a :b] [:c]) ([:a] [:b :c]) ([:a] [:b] [:c])) ; Yay! :-)
And that works, but, as noted, only when the original vector is sorted. What
if someone wanted to preserve adjacencies in an unsorted vector?
All thoughts appreciated, thanks!
Cheers,
-Paul
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