Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!willett!ForthNet
From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Vocabularies
Message-ID: <675.UUL1.3#5129@willett.UUCP>
Date: 19 Mar 90 02:52:26 GMT
Organization: Latest link in the ForthNet chain.  (Pgh, PA)
Lines: 66

Category 3,  Topic 18
Message 7         Sun Mar 18, 1990
R.BERKEY [Robert]            at 04:44 PST
 
 
 Re: Constant Numerals

Chris Waters writes, 900312:

 >    If you could, I'd like some more details about why you have
 > problems with these constants.

It was involved with a colon-definition structure that contains a table of
numbers.  In order to allow comments in the table, the compiler/interpreter
that created the table first searched the dictionary, and the search needed to
fail to correctly compile the number.

To complicate things, that particular implementation is gone.  There's now an
INTERPRETERS vocabulary that contains, among others, the ( and \ words.  That
vocabulary is used to advance the input stream pointer over the comments.

So I may not currently need NUMERALS .



 > It can't be something as simple as multiple stacks or floating
 > point, can it?  I'm just curious why there isn't an easier
 > solution to this.

The NUMERALS implementation can be simple.  It adds one vocabulary to the
compiler search order, without affecting the normal search order. An essential
element is a word that searches a single vocabulary.  As an example, the
following code adds

   ['] NUMERALS ACQUIRE

to the guts of a colon compiler.  Both the inputs and the outputs of ACQUIRE
are the same as the outputs from FIND .


   #SP WORD FIND        ( a1 false | compilation-token flag )
   ['] NUMERALS ACQUIRE
                           \ if the flag is non-zero, the search is
                           \ bypassed.  Otherwise, search NUMERALS for
                           \ the string at a1.  Outputs are the same as
                           \  FIND
   ?DUP IF
      0> IF   EXECUTE   ELSE   X,   THEN
   ELSE
      NUMBER  DOUBLE?
      IF           [COMPILE] DLITERAL
      ELSE    DROP [COMPILE] LITERAL
      THEN
   THEN


Chris,

It looks as if you're right around the corner, relative to ForthNet land.  I
can be reached in Fremont at (415) 659-1334 x352.

Robert

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