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Deterministic version of the Miller-Rabin primality test for Scala
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| //MillerRabin.scala | |
| import scala.language.implicitConversions | |
| object MillerRabin { | |
| implicit class MillerRabin(n: Long) { | |
| private lazy val asl : Array[BigInt] = if (n < 2047L) Array(2L) | |
| else if (n < 1373653L) Array(2L, 3L) | |
| else if (n < 9080191L) Array(31L, 73L) | |
| else if (n < 25326001L) Array(2L, 3L, 5L) | |
| else if (n < 3215031751L) Array(2L, 3L, 5L, 7L) | |
| else if (n < 4759123141L) Array(2L, 7L, 61L) | |
| else if (n < 1122004669633L) Array(2L, 13L, 23L, 1662803L) | |
| else if (n < 2152302898747L) Array(2L, 3L, 5L, 7L, 11L) | |
| else if (n < 3474749660383L) Array(2L, 3L, 5L, 7L, 11L, 13L) | |
| else if (n < 341550071728321L) Array(2L, 3L, 5L, 7L, 11L, 13L, 17L) | |
| else if (n < 3825123056546413051L) Array(2L, 3L, 5L, 7L, 11L, 13L, 17L, 19L, 23L) | |
| else Array(2L, 3L, 5L, 7L, 11L, 13L, 17L, 19L, 23L, 29L, 31L, 37L) | |
| private lazy val (s,d): (Int, Long) = { | |
| def sdf(s: Int, d: Long) : (Int, Long) = if(d % 2 == 0) sdf(s+1, d >>> 1) else (s,d) | |
| sdf(0, n-1) | |
| } | |
| private def millerRabin(a: BigInt): Boolean = | |
| a.modPow(d, n) != 1 && | |
| !(0L until s).view.exists(r => a.modPow(BigInt(2).pow(r.intValue())*d, n) == n - 1) | |
| implicit def isPrime: Boolean = !asl.view.exists(millerRabin) || n == 2 | |
| } | |
| } |
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