On 02.06.2009, at 17:35, Wilson MacGyver wrote:
> for example, the first 10 produces.
>
> ([2 2.8853900817779268] [4 2.8853900817779268] [8 2.8853900817779268]
> [16 3.8471867757039027] [32 5.7707801635558535] [64 9.233248261689365]
> [128 15.38874710281561] [256 26.380709319112476] [512
> 46.16624130844683] [1024 82.07331788168325])
>
> what if I want to filter so I only get pairs for which the 2nd value
> is < 10. I couldn't figure out how to get
> filter to work for pair values.
Try this:
(take 3
(filter #(< (second %) 10)
(iterate (fn [[a b]] [(* 2 a) (/ a (Math/log a))])
[2 (/ 2 (Math/log 2))])))
If you try to take 10 values, you will create an endless loop because
with the given parameters your sequence actually has less than ten
elements that satisfy the condition!
> a 2nd question is more of general clojure idiom, in trying to covert
> the following java code from michaelg's java 1 presentation
>
> private int calcSize(){
> int max = 2;
> while ((max/Math.log(max)) < size &&
> max < Integer.MAX_VALUE && max > 0){
> max *=2;
> }
> return max;
> }
>
> My first reaction was to do it using a sequence. Is this the clojure
> idiomatic way to convert a while loop from other languages?
Clojure has loops as well:
(let [size 10] ;made up
(loop [max 2]
(if (or (>= (/ max (Math/log max)) size)
(>= max Integer/MAX_VALUE)
(<= max 0))
max
(recur (* 2 max)))))
Konrad.
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