Common Lisp has several kinds of user-defined types (types, structs, classes). It is possible to write non-trivial code without ever using them, and I don't thi

Common Lisp has several kinds of user-defined types (types, structs, classes). It is possible to write non-trivial code without ever using them, and I don't think they really fit in to traditional Lisp style. Classes are fairly popular in modern Common Lisp code.