update: interfaces lecture

interfaces/04-interfaces/main.go

@@ -15,15 +15,13 @@ func main() {
 		rubik     = puzzle{title: "rubik's cube", price: 5}
 	)
 
+	// thanks to the printer interface we can add different types of values
+	// to the list.
+	//
+	// only rule: they need to implement the `printer` interface.
+	// to do that: each type needs to have a print method.
+
 	var store list
 	store = append(store, &minecraft, &tetris, mobydick, rubik)
-
-	tetris.discount(.8)
-	// printer(tetris).discount(.8)
 	store.print()
-
-	// p can store a value of any type that has a `print()` method
-	var p printer
-	p = puzzle{title: "sidewinder", price: 10}
-	p.print()
-}
+}