import java.lang.Integer._
import java.lang.Math._
import scala.collection.mutable.ArrayBuffer
class ScalaPrimes(val size:Int){
val primes = new ArrayBuffer[Int]
var cnt = 0
init
def last = primes(primes.size - 1)
private
def init {
var i = 2
val max = calcSize
val nums = new ArrayBuffer[Boolean]
for (i<-0 until max) nums += true
while (i < max && cnt < size){
val p = i
if (nums(i)){
primes += p
cnt += 1
(p until max/p).foreach((j) => nums.update(p*j,false))
}
i += 1
}
}
def calcSize = {
var max = 2
while ( (max/log(max)) < size && max < MAX_VALUE && max > 0) {
max *= 2
}
max
}
}
Saturday, May 09, 2009
JavaOne Talk: Scala Prime Sieve
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