Test encoding SML functors

SMLModules.scala

// http://stackoverflow.com/a/23019436/53974

trait ORD {
  type T
  def leq(a: T, b: T): Boolean
}

// The most direct attempt runs into limitations of refinements.
//def F(X : ORD) = new { def eq(x : X.T, y : X.T) = X.leq(x, y) && X.leq(y, x) }

// Let's avoid refinements instead by declaring the signature we want.
trait EQ {
  type T
  def eq(x : T, y : T): Boolean
}

def F(X : ORD) = new EQ { type T = X.T; def eq(x : X.T, y : X.T) = X.leq(x, y) && X.leq(y, x) }
// The REPL shows that F is given the correct type:
//   F: (X: ORD)EQ{type T = X.T}
// That is, EQ{type T = X.T} is the return type.