Clojure subvectors are "second class" data structures in terms of operations
supported on them in several ways, partly because of the O(1) way that they are
constructed and represented, and/or lack of implementations that work on the
subvector data structure.
The issue you raise is similar to this one:
http://dev.clojure.org/jira/browse/CLJ-1082
I made one of the comments there about the possibility in the future of
implementing subvec as an O(log n) operation rather than O(1), after there is
an implementation of Reduced Radix Balanced Tree vectors. If this were done,
subvectors would become just another kind of vector, and most or all of the
limitations of operations supported on them would go away.
RRB Tree vectors would also support O(log n) concatenation of two vectors.
Andy
On Dec 27, 2012, at 10:05 AM, Steven Obua wrote:
> I am using Clojure 1.4.0. It seems that reduce-kv does not work together with
> subvec.
>
> For example:
>
> (reduce-kv (fn [v index u] (+ v (* index u))) [10 3 5])
>
> results in 13, but
>
> (reduce-kv (fn [v index u] (+ v (* index u))) 0 (subvec [11 10 3 5] 1 3))
>
> yields the following exception:
>
> No implementation of method: :kv-reduce of protocol:
> #'clojure.core.protocols/IKVReduce found for class:
> clojure.lang.APersistentVector$SubVector
> [Thrown class java.lang.IllegalArgumentException]
>
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