On 17 July 2010 18:41, David Cabana <[email protected]> wrote:
> I tried to run Jame's code, but the compiler (1.2 beta) squawked at me:
> Unable to resolve symbol: indexed in this context
> [Thrown class java.lang.Exception]
>
> What do I need to pull in to pick up the "indexed" function?
Sorry, I should have mentioned you need Clojure 1.2.0 beta,
Clojure-Contrib 1.2.0 beta, and you need to include "indexed" from the
clojure.contrib.seq namespace:
(use '[clojure.contrib.seq :only (indexed)])
For version 1.1.0, it needs a little adjusting. The following code
should work under 1.1.0 (but I haven't tested this):
(use '[clojure.contrib.seq-utils :only (indexed)])
(defn convolve [ns ms]
(loop [nums (for [[i n] (indexed ns)
[j m] (indexed ms)] [(+ i j) (+ n m)])
y (vec (repeat (+ (count ns) (count ms)) 0))]
(if-let [[i s] (first nums)]
(recur (next nums) (assoc y i (+ (y i) s)))
y)))
This code will be slower, however, as it isn't using transients.
Transients are a way of speeding up manipulating data structures by
assuming you don't need to keep around the old copies.
- James
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