Common Lisp the Language
2nd Edition
The following function may be used to obtain a type specifier describing the type of a given object.
[Function]
type-of object
(type-of object) returns an implementation-dependent result:
some type of which the object is a member. Implementors
are encouraged to arrange for
type-of to return the most specific type that can be
conveniently computed and is likely to be useful to the user.
If the argument is a user-defined named
structure created by defstruct
then type-of will return the type name
of that structure.
Because the result is implementation-dependent
it is usually better
to use type-of primarily for debugging purposes;
however
in a few situations portable code requires the use of
type-of
such as when the result is to be given to the
coerce or map function.
On the other hand
often the typep function
or the typecase construct
is more appropriate than type-of.
