Scala example source code file (t2994a.scala)

This example Scala source code file (t2994a.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

mul, mul, nat, nat, naturals, succ, succ, zero, zero

The Scala t2994a.scala source code

object Naturals {
  trait NAT {
    type a[s[_ <: NAT] <: NAT, z <: NAT] <: NAT
    type v = a[SUCC, ZERO]
  }
  final class ZERO extends NAT {
    type a[s[_ <: NAT] <: NAT, z <: NAT] = z
  }
  final class SUCC[n <: NAT] extends NAT {
    type a[s[_ <: NAT] <: NAT, z <: NAT] = s[n#a[s, z]]
  }
  type _0 = ZERO
  type _1 = SUCC[_0]
  type _2 = SUCC[_1]
  type _3 = SUCC[_2]
  type _4 = SUCC[_3]
  type _5 = SUCC[_4]
  type _6 = SUCC[_5]

  
  // crashes scala-2.8.0 beta1  
  trait MUL[n <: NAT, m <: NAT] extends NAT {
    trait curry[n[_[_], _], s[_]] { type f[z <: NAT] = n[s, z] }
    type a[s[_ <: NAT] <: NAT, z <: NAT] = n#a[curry[m#a, s]#f, z]
  }

}