object PrimeConcat {
def isPrime(n: Long): Boolean = {
if (n < 2) return false
if (n % 2 == 0 && n != 2) return false
var i = 3L
while (i * i <= n) {
if (n % i == 0) return false
i += 2
}
true
}
// Concatenate two integers
def concat(a: Int, b: Int): Long = {
val s = a.toString + b.toString
s.toLong
}
def main(args: Array[String]): Unit = {
val limit = 12 // you can increase this
val primes: Seq[Int] = (2 to limit).filter(isPrime(_))
// Check pairs
for {
(p1, i) <- primes.zipWithIndex
(p2, j) <- primes.zipWithIndex
if i != j
num = concat(p1, p2)
if isPrime(num)
} {
println(s"$p1 + $p2 -> $num is prime")
}
}
}
/*
run:
2 + 3 -> 23 is prime
2 + 11 -> 211 is prime
3 + 7 -> 37 is prime
3 + 11 -> 311 is prime
5 + 3 -> 53 is prime
7 + 3 -> 73 is prime
11 + 3 -> 113 is prime
*/
