i always miss interfaces in smalltalk. sometimes i really want a guarantee that the receiver will actually listen when i send a particular message. Even if you

i always miss interfaces in smalltalk. sometimes i really want a guarantee that the receiver will actually listen when i send a particular message. Even if you don't agree with that part, interfaces are really nice because the system will tell you, "hey, you forgot to add a method to respond to X. you got the other four, but spaced out this one. you should do something about that."