Chapter 12
The Built-In Functions
Reflective Operations on Types
The following functions return information on types and test type membership. They provide
part of the implementation of the type protocol, as described
in The Type Protocol
beginning on page
49.
instance? [Function]
Tests whether an object is an instance of a type.
- Signature:
-
instance? object type⇒boolean - Arguments:
-
- object
-
An instance of
<object>. - type
An instance of
<type>.
- Values:
-
- boolean
-
An instance of
<boolean>.
- Description:
Returns true if object is a general instance of type.
subtype? [Function]
Tests whether a type is a subtype of another type.
- Signature:
-
subtype? type1 type2⇒boolean - Arguments:
-
- type1
-
An instance of
<type>. - type2
An instance of
<type>.
- Values:
-
- boolean
-
An instance of
<boolean>.
- Description:
Returns true if type1 is a subtype of type2. Subtype rules are given in
The Type Protocol
on page 49.
object-class [Function]
Returns the class of an object.
- Signature:
-
object-class object⇒class - Arguments:
-
- object
-
An instance of
<object>.
- Values:
-
- class
-
An instance of
<class>.
- Description:
Returns the class of which object is a direct instance.
all-superclasses [Function]
Returns the class precedence list of a class.
- Signature:
-
all-superclasses class⇒sequence - Arguments:
-
- class
-
An instance of
<class>.
- Values:
-
- sequence
-
An instance of
<sequence>. Each element in the sequence is an instance of<class>.
- Description:
-
Returns the class precedence list of class. This is an ordered sequence ofclass and all its superclasses, as described in
Computing the Class Precedence List
on page 54.The result sequence should never be destructively modified. Doing so may cause unpredictable behavior. If class is sealed, an implementation may choose to signal an error of type
<sealed-object-error>rather than returning the sequence of all superclasses.
direct-superclasses [Function]
Returns the direct superclasses of a class.
- Signature:
-
direct-superclasses class⇒sequence - Arguments:
-
- class
-
An instance of
<class>.
- Values:
-
- sequence
-
An instance of
<sequence>. Each element in the sequence is an instance of<class>.
- Description:
-
Returns the direct superclasses of class in a sequence. These are the classes that were passed as arguments to
makeordefine classwhen the class was created. The order of the classes in the sequence is the same as the order in which they were passed todefine classormakewhen class was created.The result sequence should never be destructively modified. Doing so may cause unpredictable behavior. If class is sealed, an implementation may choose to signal an error of type
<sealed-object-error>rather than returning the direct superclasses.
direct-subclasses [Function]
Returns the direct subclasses of a class.
- Signature:
-
direct-subclasses class⇒sequence - Arguments:
-
- class
-
An instance of
<class>.
- Values:
-
- sequence
-
An instance of
<sequence>. Each element in the sequence is an instance of<class>.
- Description:
-
Returns the direct subclasses of class in a sequence. These are the classes that have class as a direct superclass. The order of the classes in the sequence is not significant.
The result sequence should never be destructively modified. Doing so may cause unpredictable behavior. If class is sealed, an implementation may choose to signal an error of type
<sealed-object-error>rather than returning the direct subclasses.