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From: Stephen Pelc <stephen@vfxforth.com>
Newsgroups: comp.lang.forth
Subject: Re: Operator overloading?
Date: Tue, 30 Jul 2024 19:44:40 -0000 (UTC)
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On 30 Jul 2024 at 19:55:55 BST, "minforth" <minforth> wrote:

> On Tue, 30 Jul 2024 15:16:28 +0000, Stephen Pelc wrote:
>> The standard suggests/specifies that operators such as TO behave as if
>> they parse. Ignore that for the moment and define
>> 
>> variable operator
>> 
>> : to  1 operator !  ;  immediate
>> 
>> A child of VALUE is probably an immediate word that inspects OPERATOR
>> and compiles the fetch action if 0 or the store action if 1. This scheme
>> can
>> be extended to support a wide range of operators, such as +TO INCR DECR
>> and so on. MPE has used this scheme for several decades with no tech
>> support issues. If you really want to to be fussy and avoid the use of
>> the
>> "as if" rule for parsing, you can do something like (untested) the below
>> for TO. But why bother?
>> 
>> : to
>>   1 operator !  ' execute
>> ;  immediate
> 
> Thank you. So instead of wasting time on parsing during compilation- or
> interpretation time, the runtime action of an xVALUE (even when
> compiled)
> involves to walk a type-specific operator chain (a large CASE construct
> in VFX). This makes them slower when compiled, but why not.

The CASE statements are walked at compile time and so can produce
fully optimised code. Just download a VFX Forth, read the source code,
and disassemble the results.

Stephen
-- 
Stephen Pelc, stephen@vfxforth.com
MicroProcessor Engineering, Ltd. - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 (0)78 0390 3612,  +34 649 662 974
http://www.mpeforth.com
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