[GuestHNUser]

> It was obvious to me from the start that Muratori thought "dynamic polymorphism" just meant deep hierarchies of inheritance

Inheritance hierarchies aren't exclusively what he meant though. Interfaces and the whole 'prefer composition over inheritance' style of programming has the same fundamental problem Muratori is getting at: both inherently constrain a program's structure for, what he argues (and I agree with), has no benefit to the program's performance or the programmer's time. In fact, he argues that the constraints imposed by the use of inheritance/interfaces only slow programmers down.

His raw device driver example, in pt2 of their conversation, illustrates the advantage of procedural code over inheritance/interfaces. His API requires users to provide a function pointer that will be called whenever an event is raised. This API user is expected to switch over the enum values that they care to implement. This design is better than an interface that requires its members to implement read(), and write() functions because it is both more performant (no vtable overhead + compilers can make more aggressive optimizations) and more flexible (a new event can be added to the enum without requiring all the old code to be updated if they don't need to handle the new event type).