Such languages enable specialization of code based on either the class of the input object (in the case of Smalltalk), ...

Such languages enable specialization through polymorphism either based on inheritance (in the case of Smalltalk), or generic functions (in the case of Common Lisp).

tech

Goodbye, Clean Code

Correction:

>Such languages enable specialization of code based on either the class of the input object (in the case of Smalltalk), ...

should be something more like this:

>Such languages enable specialization through polymorphism either based on inheritance (in the case of Smalltalk), or generic functions (in the case of Common Lisp).