499 lines
14 KiB
Forth
499 lines
14 KiB
Forth
\ ** ficl/softwords/oo.fr
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\ ** F I C L O - O E X T E N S I O N S
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\ ** john sadler aug 1998
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\
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\ $FreeBSD$
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.( loading ficl O-O extensions ) cr
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7 ficl-vocabulary oop
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also oop definitions
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\ Design goals:
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\ 0. Traditional OOP: late binding by default for safety.
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\ Early binding if you ask for it.
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\ 1. Single inheritance
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\ 2. Object aggregation (has-a relationship)
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\ 3. Support objects in the dictionary and as proxies for
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\ existing structures (by reference):
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\ *** A ficl object can wrap a C struct ***
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\ 4. Separate name-spaces for methods - methods are
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\ only visible in the context of a class / object
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\ 5. Methods can be overridden, and subclasses can add methods.
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\ No limit on number of methods.
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\ General info:
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\ Classes are objects, too: all classes are instances of METACLASS
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\ All classes are derived (by convention) from OBJECT. This
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\ base class provides a default initializer and superclass
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\ access method
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\ A ficl object binds instance storage (payload) to a class.
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\ object ( -- instance class )
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\ All objects push their payload address and class address when
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\ executed. All objects have this footprint:
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\ cell 0: first payload cell
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\ A ficl class consists of a parent class pointer, a wordlist
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\ ID for the methods of the class, and a size for the payload
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\ of objects created by the class. A class is an object.
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\ The NEW method creates and initializes an instance of a class.
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\ Classes have this footprint:
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\ cell 0: parent class address
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\ cell 1: wordlist ID
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\ cell 2: size of instance's payload
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\ Methods expect an object couple ( instance class )
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\ on the stack.
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\ Overridden methods must maintain the same stack signature as
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\ their predecessors. Ficl has no way of enforcing this, though.
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user current-class
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0 current-class !
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ ** L A T E B I N D I N G
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\ Compile the method name, and code to find and
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\ execute it at run-time...
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\ parse-method compiles the method name so that it pushes
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\ the string base address and count at run-time.
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\
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: parse-method \ name run: ( -- c-addr u )
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parse-word
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postpone sliteral
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; compile-only
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: lookup-method ( class c-addr u -- class xt )
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2dup
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local u
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local c-addr
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end-locals
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2 pick cell+ @ ( -- class c-addr u wid )
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search-wordlist ( -- class 0 | xt 1 | xt -1 )
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0= if
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c-addr u type ." not found in "
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body> >name type
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cr abort
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endif
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;
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: exec-method ( instance class c-addr u -- <method-signature> )
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lookup-method execute
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;
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: find-method-xt \ name ( class -- class xt )
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parse-word lookup-method
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;
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\ Method lookup operator takes a class-addr and instance-addr
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\ and executes the method from the class's wordlist if
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\ interpreting. If compiling, bind late.
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\
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: --> ( instance class -- ??? )
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state @ 0= if
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find-method-xt execute
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else
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parse-method postpone exec-method
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endif
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; immediate
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ ** E A R L Y B I N D I N G
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\ Early binding operator compiles code to execute a method
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\ given its class at compile time. Classes are immediate,
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\ so they leave their cell-pair on the stack when compiling.
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\ Example:
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\ : get-wid metaclass => .wid @ ;
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\ Usage
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\ my-class get-wid ( -- wid-of-my-class )
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\
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: => \ c:( class meta -- ) run: ( -- ??? ) invokes compiled method
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drop find-method-xt compile, drop
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; immediate compile-only
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ ** I N S T A N C E V A R I A B L E S
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\ Instance variables (IV) are represented by words in the class's
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\ private wordlist. Each IV word contains the offset
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\ of the IV it represents, and runs code to add that offset
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\ to the base address of an instance when executed.
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\ The metaclass SUB method, defined below, leaves the address
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\ of the new class's offset field and its initial size on the
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\ stack for these words to update. When a class definition is
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\ complete, END-CLASS saves the final size in the class's size
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\ field, and restores the search order and compile wordlist to
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\ prior state. Note that these words are hidden in their own
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\ wordlist to prevent accidental use outside a SUB END-CLASS pair.
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\
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wordlist
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dup constant instance-vars
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dup >search ficl-set-current
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: do-instance-var
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does> ( instance class addr[offset] -- addr[field] )
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nip @ +
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;
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: addr-units: ( offset size "name" -- offset' )
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create over , +
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do-instance-var
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;
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: chars: \ ( offset nCells "name" -- offset' ) Create n char member.
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chars addr-units: ;
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: char: \ ( offset nCells "name" -- offset' ) Create 1 char member.
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1 chars: ;
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: cells: ( offset nCells "name" -- offset' )
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cells >r aligned r> addr-units:
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;
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: cell: ( offset nCells "name" -- offset' )
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1 cells: ;
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\ Aggregate an object into the class...
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\ Needs the class of the instance to create
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\ Example: object obj: m_obj
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\
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: do-aggregate
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does> ( instance class pfa -- a-instance a-class )
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2@ ( inst class a-class a-offset )
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2swap drop ( a-class a-offset inst )
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+ swap ( a-inst a-class )
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;
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: obj: ( offset class meta "name" -- offset' )
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locals| meta class offset |
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create offset , class ,
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class meta --> get-size offset +
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do-aggregate
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;
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\ Aggregate an array of objects into a class
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\ Usage example:
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\ 3 my-class array: my-array
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\ Makes an instance variable array of 3 instances of my-class
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\ named my-array.
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\
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: array: ( offset n class meta "name" -- offset' )
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locals| meta class nobjs offset |
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create offset , class ,
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class meta --> get-size nobjs * offset +
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do-aggregate
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;
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\ Aggregate a pointer to an object: REF is a member variable
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\ whose class is set at compile time. This is useful for wrapping
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\ data structures in C, where there is only a pointer and the type
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\ it refers to is known. If you want polymorphism, see c_ref
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\ in classes.fr. REF is only useful for pre-initialized structures,
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\ since there's no supported way to set one.
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: ref: ( offset class meta "name" -- offset' )
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locals| meta class offset |
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create offset , class ,
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offset cell+
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does> ( inst class pfa -- ptr-inst ptr-class )
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2@ ( inst class ptr-class ptr-offset )
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2swap drop + @ swap
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;
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\ END-CLASS terminates construction of a class by storing
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\ the size of its instance variables in the class's size field
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\ ( -- old-wid addr[size] 0 )
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\
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: end-class ( old-wid addr[size] size -- )
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swap ! set-current
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search> drop \ pop struct builder wordlist
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;
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set-current previous
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\ E N D I N S T A N C E V A R I A B L E S
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ D O - D O - I N S T A N C E
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\ Makes a class method that contains the code for an
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\ instance of the class. This word gets compiled into
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\ the wordlist of every class by the SUB method.
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\ PRECONDITION: current-class contains the class address
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\ why use a state variable instead of the stack?
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\ >> Stack state is not well-defined during compilation (there are
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\ >> control structure match codes on the stack, of undefined size
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\ >> easiest way around this is use of this thread-local variable
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\
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: do-do-instance ( -- )
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s" : .do-instance does> [ current-class @ ] literal ;"
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evaluate
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;
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ ** M E T A C L A S S
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\ Every class is an instance of metaclass. This lets
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\ classes have methods that are different from those
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\ of their instances.
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\ Classes are IMMEDIATE to make early binding simpler
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\ See above...
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\
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:noname
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wordlist
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create
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immediate
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0 , \ NULL parent class
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dup , \ wid
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3 cells , \ instance size
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ficl-set-current
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does> dup
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; execute metaclass
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metaclass drop current-class !
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do-do-instance
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\
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\ C L A S S M E T H O D S
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\
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instance-vars >search
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create .super ( class metaclass -- parent-class )
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0 cells , do-instance-var
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create .wid ( class metaclass -- wid ) \ return wid of class
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1 cells , do-instance-var
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create .size ( class metaclass -- size ) \ return class's payload size
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2 cells , do-instance-var
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previous
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: get-size metaclass => .size @ ;
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: get-wid metaclass => .wid @ ;
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: get-super metaclass => .super @ ;
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\ create an uninitialized instance of a class, leaving
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\ the address of the new instance and its class
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\
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: instance ( class metaclass "name" -- instance class )
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locals| meta parent |
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create
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here parent --> .do-instance \ ( inst class )
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parent meta metaclass => get-size
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allot \ allocate payload space
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;
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\ create an uninitialized array
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: array ( n class metaclass "name" -- n instance class )
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locals| meta parent nobj |
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create nobj
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here parent --> .do-instance \ ( nobj inst class )
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parent meta metaclass => get-size
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nobj * allot \ allocate payload space
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;
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\ create an initialized instance
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\
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: new \ ( class metaclass "name" -- )
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metaclass => instance --> init
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;
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\ create an initialized array of instances
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: new-array ( n class metaclass "name" -- )
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metaclass => array
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--> array-init
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;
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\ Create an anonymous initialized instance from the heap
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: alloc \ ( class metaclass -- instance class )
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locals| meta class |
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class meta metaclass => get-size allocate ( -- addr fail-flag )
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abort" allocate failed " ( -- addr )
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class 2dup --> init
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;
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\ Create an anonymous array of initialized instances from the heap
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: alloc-array \ ( n class metaclass -- instance class )
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locals| meta class nobj |
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class meta metaclass => get-size
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nobj * allocate ( -- addr fail-flag )
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abort" allocate failed " ( -- addr )
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nobj over class --> array-init
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class
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;
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\ create a proxy object with initialized payload address given
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: ref ( instance-addr class metaclass "name" -- )
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drop create , ,
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does> 2@
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;
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\ create a subclass
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: sub ( class metaclass "name" -- old-wid addr[size] size )
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wordlist
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locals| wid meta parent |
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parent meta metaclass => get-wid
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wid wid-set-super
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create immediate
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here current-class ! \ prep for do-do-instance
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parent , \ save parent class
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wid , \ save wid
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here parent meta --> get-size dup , ( addr[size] size )
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metaclass => .do-instance
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wid ficl-set-current -rot
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do-do-instance
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instance-vars >search \ push struct builder wordlist
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;
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\ OFFSET-OF returns the offset of an instance variable
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\ from the instance base address. If the next token is not
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\ the name of in instance variable method, you get garbage
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\ results -- there is no way at present to check for this error.
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: offset-of ( class metaclass "name" -- offset )
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drop find-method-xt nip >body @ ;
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\ ID returns the string name cell-pair of its class
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: id ( class metaclass -- c-addr u )
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drop body> >name ;
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\ list methods of the class
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: methods \ ( class meta -- )
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locals| meta class |
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begin
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class body> >name type ." methods:" cr
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class meta --> get-wid >search words cr previous
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class meta metaclass => get-super
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dup to class
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0= until cr
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;
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\ list class's ancestors
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: pedigree ( class meta -- )
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locals| meta class |
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begin
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class body> >name type space
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class meta metaclass => get-super
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dup to class
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0= until cr
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;
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\ decompile a method
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: see ( class meta -- )
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metaclass => get-wid >search see previous ;
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set-current
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\ E N D M E T A C L A S S
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\ META is a nickname for the address of METACLASS...
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metaclass drop
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constant meta
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\ SUBCLASS is a nickname for a class's SUB method...
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\ Subclass compilation ends when you invoke end-class
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\ This method is late bound for safety...
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: subclass --> sub ;
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\ \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
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\ ** O B J E C T
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\ Root of all classes
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:noname
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wordlist
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create immediate
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0 , \ NULL parent class
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dup , \ wid
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0 , \ instance size
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ficl-set-current
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does> meta
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; execute object
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object drop current-class !
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do-do-instance
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\ O B J E C T M E T H O D S
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\ Convert instance cell-pair to class cell-pair
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\ Useful for binding class methods from an instance
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: class ( instance class -- class metaclass )
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nip meta ;
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\ default INIT method zero fills an instance
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: init ( instance class -- )
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meta
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metaclass => get-size ( inst size )
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erase ;
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\ Apply INIT to an array of NOBJ objects...
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\
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: array-init ( nobj inst class -- )
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0 dup locals| &init &next class inst |
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\
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\ bind methods outside the loop to save time
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\
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class s" init" lookup-method to &init
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s" next" lookup-method to &next
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drop
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0 ?do
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inst class 2dup
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&init execute
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&next execute drop to inst
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loop
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;
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\ free storage allocated to a heap instance by alloc or alloc-array
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\ NOTE: not protected against errors like FREEing something that's
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\ really in the dictionary.
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: free \ ( instance class -- )
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drop free
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abort" free failed "
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;
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\ Instance aliases for common class methods
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\ Upcast to parent class
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: super ( instance class -- instance parent-class )
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meta metaclass => get-super ;
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: pedigree ( instance class -- )
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object => class
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metaclass => pedigree ;
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: size ( instance class -- sizeof-instance )
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object => class
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metaclass => get-size ;
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: methods ( instance class -- )
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object => class
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metaclass => methods ;
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\ Array indexing methods...
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\ Usage examples:
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\ 10 object-array --> index
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\ obj --> next
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\
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: index ( n instance class -- instance[n] class )
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locals| class inst |
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inst class
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object => class
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metaclass => get-size * ( n*size )
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inst + class ;
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: next ( instance[n] class -- instance[n+1] class )
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locals| class inst |
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inst class
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object => class
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metaclass => get-size
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inst +
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class ;
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: prev ( instance[n] class -- instance[n-1] class )
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locals| class inst |
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inst class
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object => class
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metaclass => get-size
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inst swap -
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class ;
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set-current
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\ E N D O B J E C T
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previous definitions
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