Mersenne primes: Difference between revisions

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=={{header|Scala}}==

<lang Scala>~~object MersennePrimes extends App {~~

object MersennePrimes extends App {

import Stream._

~~def~~ primeSieve(~~s: Stream[Int]~~)~~: Stream[Int] =~~

val primes = primeSieve(LazyList.from(2))

s.head #:: primeSieve(s.tail filter { ~~_ % s.head != 0 })~~

val primes = primeSieve(from(2))

def mersenne(p: Int): BigInt = (BigInt(2) pow p) - 1

~~def~~ ~~s(mp: BigInt, p: Int): BigInt = {~~ if (p == 1) 4 else ((s(mp, p - 1) pow 2) - 2) % mp }

val upbPrime = 9941

def primeSieve(s: LazyList[Int]): LazyList[Int] =

s.head #:: primeSieve(s.tail filter {

_ % s.head != 0

})

def mersenne(p: Int): BigInt = (BigInt(2) pow p) - 1

def s(mp: BigInt, p: Int): BigInt = {

if (p == 1) 4 else ((s(mp, p - 1) pow 2) - 2) % mp

}

println(s"Finding Mersenne primes in M[2..$upbPrime]")

((primes takeWhile (_ <= upbPrime)).~~par~~ map { p => (p, mersenne(p)) }

((primes takeWhile (_ <= upbPrime)).map { p => (p, mersenne(p)) }

map { p => if (p._1 == 2) (p, 0) else (p, s(p._2, p._1 - 1)) } filter { ~~_._2 == 0 })~~

map { p => if (p._1 == 2) (p, 0) else (p, s(p._2, p._1 - 1)) } filter {

_._2 == 0

})

.foreach { p =>

println(s"prime M${(p._1)._1}: " +

println(s"prime M${(p._1)._1}: " + {

{ if ((p._1)._1 < 200) (p._1)._2 else s"(${(p._1)._2.toString.~~size~~} digits)" })

if ((p._1)._1 < 200) (p._1)._2 else s"(${(p._1)._2.toString.length} digits)"

})

}

println("That's All Folks!")

}

}</lang>

</lang>

=={{header|Sidef}}==

Uses the ''is_mersenne_prime()'' function from [https://metacpan.org/pod/Math::Prime::Util::GMP Math::Prime::Util::GMP].