to determine whether a number is a prime

isPrime.scala

def isPrime(i: Int) =
  if (i <= 1)
    false
  else if (i == 2)
    true
  else
    !(2 to i/2).exists(x => i % x == 0)         //> isPrime: (i: Int)Boolean

isPrime(2)                                //> res0: Boolean = true
isPrime(3)                                //> res1: Boolean = true
isPrime(4)                                //> res2: Boolean = false
isPrime(5)                                //> res3: Boolean = true
isPrime(6)                                //> res4: Boolean = false
isPrime(7)                                //> res5: Boolean = true
isPrime(8)                                //> res6: Boolean = false
isPrime(9)                                //> res7: Boolean = false
isPrime(10)                               //> res8: Boolean = false
isPrime(11)                               //> res9: Boolean = true