看不到视界和上界之间的区别

Question

在以下示例中，我使用的是view bound和upper bound。代码完全相同，只是<%和<:的符号不同。 view bound和upper bound之间有什么区别？

scala> class Person[T <% Ordered[T]](val fn:T, val ln:T) {
     | def greater = if (fn > ln) fn else ln
     | }
defined class Person

scala> val p1 = new Person("manu", "chadha")
p1: Person[String] = Person@31b91435

scala> val p2 = new Person("anita", "chadha")
p2: Person[String] = Person@61e0f9b9

scala> p1.greater
res3: String = manu

scala> p2.greater
res4: String = chadha

scala> class Person2[T <: Ordered[T]](val fn:T, val ln:T) {
     | def greater = if (fn > ln) fn else ln
     | }
defined class Person2

scala> val p3 = new Person("manu", "chadha")
p3: Person[String] = Person@7c50709a

scala> val p4 = new Person("anita", "chadha")
p4: Person[String] = Person@1d686622

scala> p3.greater
res5: String = manu

scala> p4.greater
res6: String = chadha

scala>