Node:CREATE..DOES> details, Next:Advanced does> usage example, Previous:CREATE..DOES> applications, Up:User-defined Defining Words
CREATE..DOES>
DOES>
compilation colon-sys1 -- colon-sys2 ; run-time nest-sys -- core ``does''
This means that you need not use CREATE
and DOES>
in the
same definition; you can put the DOES>
-part in a separate
definition. This allows us to, e.g., select among different DOES>
-parts:
: does1 DOES> ( ... -- ... ) ... ; : does2 DOES> ( ... -- ... ) ... ; : def-word ( ... -- ... ) create ... IF does1 ELSE does2 ENDIF ;
In this example, the selection of whether to use does1
or
does2
is made at definition-time; at the time that the child word is
CREATE
d.
In a standard program you can apply a DOES>
-part only if the last
word was defined with CREATE
. In Gforth, the DOES>
-part
will override the behaviour of the last word defined in any case. In a
standard program, you can use DOES>
only in a colon
definition. In Gforth, you can also use it in interpretation state, in a
kind of one-shot mode; for example:
CREATE name ( ... -- ... ) initialization DOES> code ;
is equivalent to the standard:
:noname DOES> code ; CREATE name EXECUTE ( ... -- ... ) initialization
>body
xt -- a_addr core ``>body''
Get the address of the body of the word represented by xt (the
address of the word's data field).