Inconsistent behavior of the default comparison routine

[shirok]

Comparing classes sometimes work:

gosh> (compare <integer> <string>)
-1

But sometimes not:

gosh> (compare <integer> <real>)
*** ERROR: Object #<class <integer>> and #<class <real>> are not comparable

[shirok]

This has to do the fact that metaclass hierarchy. When (class-of x) and (class-of y) has a subtype relationship, compare calls the superclass's built-in compare callback. Otherwise, it uses the fallback code.