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January 1992 February
(Pcyerk Listing Four, continued.)
\ ......................
\ ** DEFERRED BINDING **
\ ......................
\ Deferred binding allow you to specify the object at runtime,
\ rather than at compile time.
\ { Starts deferred binding. He assumes there's a method # on
\ top of the method stack. He copies that as a literal into
\ inline code (along with an mpush) .
: {
state@
if \ We are compiling
compile (lit) \ Compile literal
mPoP ,t
\ Get method #
compile mpush \ Compile mpush code
endif \ Interpreting--do nothing
; immediate
\ ) Concludes a deferred method. He assumes there will be
\ (at runtime) a method # on top of the method stack and an
\ object pointer atop the data stack. He pushes the object
\ pointer onto the object stack, finds the method, and executes
\ it.
: 1
opush \ Push object pointer
exec-ob j \ Execute it
I
\ .......................
\ ** PATCHES AND MISC. **
\ .......................
\ Following code is the patch to interpret.
\ Allows system to recognize methods and instance variables.
\ NOTE: When we get here, literal? has left 2 zeros on stack.
\ For uniformity's sake. ..we pass them on along.
:
2drop \ Clear stack
\ See if the item in question is a method. If so, leave the
\ method id # on the method stack
here methname-find dup
-1
if mpush exit \ Push the method #
else drop
endif
\ Not a method -- see if it's an ivar
here search-ivar dup
-1
if ?comp \ GOTTA be compiling
compile (lit) \ Compile ivar value
, t
compile (do-ivar) \ Compile ivar handler
exit
else drop
endif
(Zisting continues on page 21 .)
18 Forth Dimensions