// Courtesy Ronnie Collinson

def isPrime(n: Int) =
  List.range(2, n) forall (x => n % x != 0)


val l9 = List.range(1, 10)

val pairs = l9.flatMap(i => List.range(1, i).map(x => (i, x)))

val primePairs = pairs.filter(pair => isPrime(pair._1 + pair._2)) 


/*
List.range(1, 10) 
.flatMap(i => List.range(1, i).map(x => (i, x))) 
.filter(pair => isPrime(pair._1 + pair._2)) 
*/