I agree with the claim that knowing CLOS is useful to read code bases. Where I think we differ is that I don’t consider CLOS a part of the language itself. I co

I agree with the claim that knowing CLOS is useful to read code bases. Where I think we differ is that I don’t consider CLOS a part of the language itself. I consider it a part of a particular implementation of the language. You can be a fluent and prolific CL programmer without ever writing any code that relies on CLOS, defstruct or defclass, etc. The big difference between C++ and CL in this particular instance is that you can’t write C++ without writing or using classes/structs. For example, using STL almost always involves using or writing custom comparator “classes”. Even if you choose to go with lambdas, the whole concept of a container is object oriented. In CL, you can, if you want, stick with lists all the way down without ever touching defclass/defstruct at all. An equivalent abstraction level of the C++ code would only use integral data types. Whereas in CL those types are part of the language.