Question

I’m trying to load a Scala file inside the interpreter:

trait MyOrdered {
  def <(that: MyInt):Boolean = compare(that) < 0
  def >(that: MyInt):Boolean = compare(that) > 0
  def <=(that: MyInt):Boolean = compare(that) < 0 || this == that
  def >=(that: MyInt):Boolean = compare(that) > 0 || this == that
  def compare(that: MyInt): Int
}

class MyInt(val value: Int) extends MyOrdered {
  def compare(that: MyInt) =
    if (this.value < that.value) -1 
    else if (this.value == that.value) 0
    else 1
}


object App extends Application{
  val a = new MyInt(2)
  val b = new MyInt(4)
  println(a < b)
  println(a > b)
}

But I receive a silly error:

Loading traits.scala...
<console>:8: error: not found: type MyInt
         def <(that: MyInt):Boolean = compare(that) < 0
                     ^
<console>:12: error: not found: type MyInt
         def compare(that: MyInt): Int

How can I make the interpreter know the MyInt class, which is defined down the road?

Answer 1

I think you want the behavior of :paste. :load behaves as if you are typing in the interpreter i.e., it interprets as soon as it finds the closing braces. You can emulate the :paste by wrapping your code in some object like this:

object Test {
  trait MyOrdered {
def <(that: MyInt):Boolean = compare(that) < 0
def >(that: MyInt):Boolean = compare(that) > 0
def <=(that: MyInt):Boolean = compare(that) < 0 || this == that
def >=(that: MyInt):Boolean = compare(that) > 0 || this == that
def compare(that: MyInt): Int
}

class MyInt(val value: Int) extends MyOrdered {
  def compare(that: MyInt) =
  if (this.value < that.value) -1 
  else if (this.value == that.value) 0
  else 1
}


object App extends Application{
  val a = new MyInt(2)
  val b = new MyInt(4)
  println(a < b)
  println(a > b)
 }
}

Now you can use it as you want after :load Test.scala and import Test._