Re: Forth programming style...

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: Forth programming style...
Date	2015-07-22 12:51 -0700
Organization	A noiseless patient Spider
Message-ID	<87si8gt1hs.fsf@jester.gateway.sonic.net> (permalink)
References	(2 earlier) <1a2e838f-e3f7-4f99-a321-9a02c1d6d6cb@googlegroups.com> <84a2fcaf-807e-46a0-8c38-e68515a83c67@googlegroups.com> <654e3729-7fce-4a04-a707-a0d5f7ab6050@googlegroups.com> <55357ad6-5a4b-4ef6-b46b-7d05f9c5b3cf@googlegroups.com> <4a7026e6-18ea-4f7c-a255-7874baba3769@googlegroups.com>

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humptydumpty <ouatubi@gmail.com> writes:
> push ( addr len delta --  ;inside buffer at ADDR LEN push block of LEN-DELTA
> size from ADDR to ADDR+DELTA )
> I wanted to experiment with locals, so first definition was:
> : push  { addr len delta -- }   addr addr delta + len delta - cmove> ; ...
> Analyzing version using locals, I observed I was to much attracted to
> use the thoughtless way of doing, it was so easy to do it, even not
> observed the opportunity to use '/string'!

Locals are more useful when there are enough live values that it's hard
to get at them with stack operations.  Classic example is multiplying
two complex numbers, x=a+bi and y=c+di, so x*y = (ac-bd) + i(ad+bc):

  : z* { a b c d -- re im } a c * b d - a d * b c + ;

that can be done with stack juggling but who wants to bother?

The genius of Forth was realizing this situation doesn't occur all that
often.  But it does sometimes occur.  Chuck's code uses VARIABLEs rather
freely to deal with it when it arises.  That means you either burn RAM
by permanently allocating a cell for each such variable even when
they're not simultaneously in use, or else you have to carefully track
which ones might overlap during nested calls.  You also must handle the
possibility of such variables being used by multiple words.  Better is
to use stack-like allocation for them, plus temporary names, and that
which is what locals amounts to.

Thread

Forth programming style... Mux <Yvo.Zoer@gmail.com> - 2015-07-21 15:40 -0700
  Re: Forth programming style... Julian Fondren <ayrnieu@gmail.com> - 2015-07-21 17:28 -0700
    Re: Forth programming style... Julian Fondren <ayrnieu@gmail.com> - 2015-07-21 17:39 -0700
      Re: Forth programming style... Mark Wills <markwills1970@gmail.com> - 2015-07-22 00:48 -0700
        Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-07-21 22:25 -1000
          Re: Forth programming style... onewingedshark@gmail.com - 2015-07-22 15:13 -0700
            Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-07-22 13:24 -1000
            Re: Forth programming style... stephen@mpeforth.com (Stephen Pelc) - 2015-07-23 08:28 +0000
        Re: Forth programming style... Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-22 02:38 -0700
          Re: Forth programming style... Mark Wills <markwills1970@gmail.com> - 2015-07-22 03:14 -0700
            Re: Forth programming style... humptydumpty <ouatubi@gmail.com> - 2015-07-22 03:45 -0700
              Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-07-22 08:37 -1000
              Re: Forth programming style... Paul Rubin <no.email@nospam.invalid> - 2015-07-22 12:51 -0700
                Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-07-22 10:14 -1000
                Re: Forth programming style... anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-23 06:23 +0000
                Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-23 16:59 -0700
                Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-23 20:18 -0700
                Re: Forth programming style... "HAA" <someone@microsoft.com> - 2015-07-28 21:06 +1000
                Re: Forth programming style... "Alex McDonald" <blog@rivadpm.com> - 2015-07-28 12:38 +0100
            Re: Forth programming style... "HAA" <someone@microsoft.com> - 2015-07-23 00:02 +1000
            Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-22 21:21 -0700
              Re: Forth programming style... "WJ" <w_a_x_man@yahoo.com> - 2015-07-23 09:05 +0000
                Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-23 16:47 -0700
                Re: Forth programming style... Mark Wills <markwills1970@gmail.com> - 2015-07-24 01:24 -0700
                Re: Forth programming style... franck.bensusan@gmail.com - 2015-07-24 03:48 -0700
                Re: Forth programming style... Paul Rubin <no.email@nospam.invalid> - 2015-07-24 18:15 -0700
                Re: Forth programming style... "HAA" <someone@microsoft.com> - 2015-08-01 13:21 +1000
            Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-22 21:48 -0700
            Re: Forth programming style... Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-22 22:28 -0700
              Re: Forth programming style... Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-02 00:43 +0200
            Re: Forth programming style... Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-02 00:22 +0200
              Re: Forth programming style... hughaguilar96@gmail.com - 2015-08-01 16:41 -0700
                Re: Forth programming style... "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-08-01 22:01 -0400
              Re: Forth programming style... anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-02 05:50 +0000
                Re: Forth programming style... Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-02 16:33 +0200
            Re: Forth programming style... "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-08-01 22:04 -0400
              Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-08-02 08:54 -0500
                Re: Forth programming style... "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-08-03 04:51 -0400
                Re: Forth programming style... "Elizabeth D. Rather" <erather@forth.com> - 2015-08-03 17:36 -0500
        Re: Forth programming style... anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-22 10:16 +0000
      Re: Forth programming style... mhx@iae.nl - 2015-07-22 10:02 -0700
    Re: Forth programming style... anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-07-22 10:09 +0000
  Re: Forth programming style... Syd Rumpo <usenet@nononono.co.uk> - 2015-07-22 12:16 +0100
    Re: Forth programming style... Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-07-22 07:59 -0700
  Re: Forth programming style... glidedog@gmail.com - 2015-07-23 04:24 -0700
  Re: Forth programming style... "Ala'a Alawi" <amalawi@gmail.com> - 2015-07-23 19:32 -0700
    Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-23 21:33 -0700
      Re: Forth programming style... borota@gmail.com - 2015-07-23 22:09 -0700
        Re: Forth programming style... hughaguilar96@gmail.com - 2015-07-23 22:57 -0700
        Re: Forth programming style... "Ala'a Alawi" <amalawi@gmail.com> - 2015-07-24 09:26 -0700
      Re: Forth programming style... "Ala'a Alawi" <amalawi@gmail.com> - 2015-07-24 09:26 -0700

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