5 - Forth Interest Group
5 - Forth Interest Group
5 - Forth Interest Group
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NOW . . . . ;<br />
Define an immedia'te word which<br />
executes by the interpretation<br />
of sequential compilation<br />
addresses, and will execute<br />
when encountered during<br />
compilation.<br />
CREATE <br />
As in FORTH-79.<br />
n CONSTANT <br />
As in FORTH-79.<br />
VARIABLE <br />
As in FORTH-79.<br />
VOCABULARY <br />
As in FORTH-79, but each<br />
defined<br />
immediate.<br />
vocabulary is<br />
When the programmer creates new<br />
word types, a significantly different<br />
syntax is used, as compared to<br />
FORTH- 7 9 .<br />
DOES> . . . . ;<br />
Begin the nameless run-time<br />
high-level code for words to<br />
be defined by .<br />
BUILDS> . . . . ;<br />
<br />
Define which, when later<br />
executed will itself create a<br />
word definition. The code<br />
after executes after<br />
creating the new dictionary<br />
header for to aid par-<br />
ameter storage. The previous<br />
run-time code is assigned to<br />
each word created by<br />
.<br />
When new classes of words are created<br />
with their run-time execution<br />
expressed by machine code, their<br />
defining word is created thusly:<br />
CODE> . . . . ENG-CODE<br />
Begin the nameless run-time<br />
machine code for words to be<br />
defined by .<br />
BUILDS> . . . . ;<br />
<br />
Define which, when later<br />
executed will itself create a<br />
word definition. The code<br />
after executes after<br />
creating the new dictionary<br />
header for to aid<br />
parameter storage. The<br />
previous run-time code is<br />
assigned to each word <br />
created by .<br />
THE METHOD<br />
We will follow the method of the<br />
honey bee. To propagate the colony<br />
the bees need a queen bee. An ordi-<br />
nary bee is fed special hormones to<br />
become a queen bee. By regulating<br />
this process the colony regulates its<br />
growth.<br />
Our queen bee will be BUILDS) .<br />
It is originally created as a colon<br />
definition. Then it is converted<br />
into a new type of word that creates<br />
words which always create. This form<br />
uses parameters to create a dictionary<br />
entry and then passes control to the<br />
users code which specifies completion<br />
of the entry.<br />
We will break the CREATE DOES><br />
construct into two parts. The creat-<br />
ing part will be called BUILDS> with<br />
the right pointer emphasizing that<br />
the following word 'builds' other<br />
Page 124 FORTH DIMENSIONS II/5