Class Hierarchy

The data structure of objects are defined by classes, and their behaviors are defined by methods in the classes. In EusLisp, a few dozens of classes have already been defined in tree structured hierarchy as depicted in fig. 4. You can browse the real inheritance structure by the class-hierarchy function. The class 'object' at the leftmost is the ultimate super-class of all the classes in EusLisp. User-defined classes can inherit any of these built-in classes.

Figure 4: Hierarchy of Predefined Classes

A class is defined the defclass macro or by the defstruct macro.

 (defclass class-name &key :super   class 

:slots 		 () 

:metaclass 		 metaclass 

:element-type 		 t 

:size  -1

) 

(defstruct struct-name slots...) 

(defstruct (struct-name [struct-options ...]) 

         (slot-name1 [slot-option...]) 

         (slot-name2 [slot-option...]) 

          ...) 

Methods are defined by the defmethod special form. Defmethod can appear any times for a particular class.

 (defmethod class-name  

(:method-name1 (parameter...) . body1) 

(:method-name2 (parameter...) . body2) 

...) 

Field definitions for most of built-in classes are found in *eusdir*/c/eus.h header file. (describe) class) gives the description of all the slots in class, namely, super class, slot names, slot types, method list, and so on. Definitions of built-in classes follow. Note that the superclass of class object is NIL since it has no super class.

 (defclass object :super NIL :slots ()) 

 (defclass cons :super object :slots (car cdr)) 

 (defclass propertied-object :super object 

  :slots (plist))   ;property list 

 (defclass symbol :super propertied-object 

  :slots (value   ;specially bound value 


vtype 		                ;const(0),var(1),special(2)  


function 		             ;global func def 


pname 		  ;print name string 


homepkg)) 		            ;home package 

 (defclass foreign-pod :super symbol 

  :slots (podcode   ;entry code 


paramtypes 		      ;type of arguments  


resulttype)) 

 (defclass package :super propertied-object 

  :slots (names   ;list of package name and nicknames


uses 		  ;spread use-package list 


symvector 		 ;hashed obvector 


symcount 		  ;number of interned symbols 


intsymvector 		 ;hashed obvector of internal symbols 


intsymcount 		  ;number of interned internal symbols 


shadows 		 ;shadowed symbols 


used-by)) 		  ;packages using this package 

 (defclass stream :super propertied-object   

  :slots (direction   ;:input or :output, nil if closed 


buffer 		  ;buffer string 


count 		 ;current character index 


tail)) 		  ;last character index 

 (defclass file-stream :super stream 

  :slots (fd   ;file descriptor (integer)


fname))		 ;file name str; qid for msgq 

 (defclass broadcast-stream :super stream

  :slots (destinations))   ;streams to which output is delivered 

 (defclass io-stream :super propertied-object

:slots (instream outstream)) 

 (defclass socket-stream :super io-stream

:slots (address))   ; socket address 

 (defclass read-table  :super propertied-object 

       :slots (syntax   ; byte vector representing character types 

; 0:illegal, 1:white, 2:comment, 3:macro

; 4:constituent, 5:single_escape

; 6:multi_escape, 7:term_macro, 8:nonterm_macro 


macro 		 ;character macro expansion function


dispatch-macro)) 

 (defclass array :super propertied-object 

  :slots (entity  ;simple vector storing array entity 


rank 		 ;number of dimensions: 0-7 


fillpointer 		    ;pointer to push next element 


offset 		    ;offset for displaced array 


dim0,dim1,dim2,dim3,dim4,dim5,dim6))  ;dimensions 

 (defclass metaclass :super propertied-object 

    :slots   (name    ;class name symbol 


super 		   ;super class 


cix 		      ;class id 


vars 		     ;var name vector including inherited vars 


types 		    ;type vector of object variables 


forwards 		  ;components to which messages are forwarded 


methods)) 		  ;method list 

 (defclass vectorclass :super metaclass  

  :slots (element-type    ;vector element type 0-7


size)) 		  ;vector size; 0 if unspecified 

 (defclass cstructclass :super vectorclass  

  :slots (slotlist))    ;cstruct slot descriptors

 (defclass vector :super object :slots (size)) 

 (defclass float-vector :super vector :element-type :float) 

 (defclass string :super vector :element-type :char) 

 (defclass hash-table :super propertied-object 

   :slots   (lisp::key  ;hashed key vector


value 		 ; value vector


size 		 ; the size of the hash table


count 		 ; number of elements entered in the table


lisp::hash-function 		 


lisp::test-function 


lisp::rehash-size 


lisp::empty  lisp::deleted 		) 

 (defclass pathname :super propertied-object 

   :slots   (lisp::host device  ; not used


directory 		 ; list of directories


name 		 ; file name before the last "."


type 		 ; type field after the last "."


lisp::version) 		 ; not used 

 (defclass label-reference    ;for reading #n=, #n# objects 

  :super object 

:slots (label value unsolved next)) 

 (defclass compiled-code :super object 

   :slots   (codevector 


quotevector 


type   ;0=func, 1=macro, 2=special 


entry)) 		  ;entry offset  

 (defclass closure :super compiled-code 

:slots (env1 env2));environment 

 (defclass foreign-code  :super compiled-code  

   :slots   (paramtypes    ;list of parameter types


resulttype)) 		 ;function result type 

 (defclass load-module  :super compiled-code  

   :slots  (symbol-table   ;hashtable of symbols defined 


object-file 		 ;name of the object file loaded, needed for unloading 


handle 		 ;file handle returned by ''dlopen''