Polymorphic copy: Difference between revisions

=={{header|Forth}}==

{{works with|4tH|3.62.1}}

{{trans|Aikido}}

There are numerous, mutually incompatible object oriented frameworks for Forth. This one works with the FOOS preprocessor extension of [[4tH]].

<lang forth>include lib/memcell.4th

include 4pp/lib/foos.4pp

( a1 -- a2)

:token fork dup allocated dup (~~alloc) swap >r swap over r> smove ;

\ allocate an empty object

:: T() \ super class T

class

method: print \ print message

method: clone \ clone yourself

end-class {

\ implementing methods

:method { ." class T" cr } ; defines print

fork defines clone ( -- addr)

}

;

:: S() \ class S

extends T() \ derived from T

end-extends { \ print message

:method { ." class S" cr } ; defines print

} \ clone yourself

;

new T() t \ create a new object t

new S() s \ create a new object s

." before copy" cr

t => print \ use "print" methods

s => print

t => clone to tcopy \ cloning t, spawning tcopy

s => clone to scopy \ cloning s, spawning scopy

." after copy" cr

tcopy => print \ use "print" methods

scopy => print</lang>