While upper type bounds limit a type to a subtype of another type, lower type bounds declare a type to be a supertype of another type. The term B >: A
expresses that the type parameter B
or the abstract type B
refer to a supertype of type A
. In most cases, A
will be the type parameter of the class and B
will be the type parameter of a method.
This is a companion discussion topic for the original entry at http://docs.scala-lang.org//tutorials/tour/lower-type-bounds.html.html