Scala: how to get random element form given list

Question

I want to pick random element from given list:

  def randomAlphaNumericChar(): Char = {
    val ALPHA_NUMERIC_STRING = "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ0123456789".toCharArray
    Gen.oneOf(ALPHA_NUMERIC_STRING)
  }

So currently this now compile:

type mismatch; found : org.scalacheck.Gen[Char] required: Char Gen.oneOf(ALPHA_NUMERIC_STRING)

The exception is really clear. You expect the function to return Char while the method you're using returns Gen[Char]. Fix one of the above. — Avihoo Mamka
– Avihoo Mamka, Commented Jul 10, 2016 at 8:50
@AvihooMamka Nitpick - It's not an exception, it's a compile time error. — Yuval Itzchakov
– Yuval Itzchakov, Commented Jul 10, 2016 at 11:41

haluk · Accepted Answer · 2016-07-10 11:20:37Z

1

  def randomAlphaNumericChar(): Char = {
  /*
     ASCII Codes
     [0-9]: (48 to 57)
     [A-Z]: (65 to 90)
     [a-z]: (97 to 122)
  */
    val alphabet = (48 to 57) union (65 to 90) union (97 to 122)
    val i = scala.util.Random.nextInt(alphabet.size)
    alphabet(i).toChar
  }

answered Jul 10, 2016 at 11:20

haluk

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Comments

elm · Accepted Answer · 2016-07-10 13:46:45Z

1

For

val xs = ('a' to 'z') ++ ('A' to 'Z') ++ (1 to 9)

try

xs.maxBy(_ => scala.util.Random.nextInt)

Here maxBy applies a function to each element of the collection and then selects the maximum value returned by the function applied to each element. In this case the function is a random value returned from Random.nextInt.

answered Jul 10, 2016 at 13:46

elm

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Comments

hipjim · Accepted Answer · 2016-07-10 10:51:03Z

0

Something like this will work

def randomAlphaNumericChar(): Char = {
    val ALPHA_NUMERIC_STRING = "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ0123456789".toList
    scala.util.Random.shuffle(ALPHA_NUMERIC_STRING).head
}

answered Jul 10, 2016 at 10:51

hipjim

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