9.7.2 Sorting Methods

Now, with the idea of the class precedence list, we can state precisely how the possible methods are sorted when more than one of the methods of a generic function are applicable to the call arguments.

The rules are that

• the applicable methods are sorted in order of specificity, and the most specific method is used first, then the next if that method calls next-method, and so on
• a method M1 is more specific than another method M2 if the first specializing class that differs, between the definitions of M1 and M2, is more specific, in M1’s definition, for the corresponding actual call argument, than the specializing class in M2’s definition
• a class C1 is more specific than another class C2, for an object of actual class C, if C1 comes before C2 in C’s class precedence list.