Implementation Role Feature 18

Title

Roles can be grouped and constrained together

Description

Role groups allow to constrain how often a set of role types can be played.

Implementation

Consider for example the following code:

// creating two player objects
val acc1 = new Account()
val acc2 = new Account()

// and a new compartment instance
new Transaction {
  // with two roles
  class Source
  class Target

  val source = new Source
  val target = new Target

  // this role group enforces XOR between the two given role types, i.e.
  // that a player is allowed to play exactly one of them (first tuple of integers)
  // and that both roles have to played, i.e. in sum two (second tuple).
  RoleGroup("Transaction").containing[Source, Target](1, 1)(2, 2)

  // this will work
  RoleGroupsChecked {
    acc1 play source
    acc2 play target
  }

  // this will throw a RuntimeException because the Target role is not played at all anymore
  RoleGroupsChecked {
    acc2 drop target
  }

  // this will throw a RuntimeException as well because the XOR restriction is violated
  RoleGroupsChecked {
    acc1 play target
  }
}

Additional hints

None.