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Groups > comp.lang.forth > #3625

Re: macro expansion ?

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On 2011-06-29 12:25:33 +0100, Anton Ertl said:

> Chris Hinsley <chris.hinsley@gmail.com> writes:
>> From the recent thread on IMMEDIATE I quote this word:
>> 
>> \ macros
>> : MACRO ( "name" <ccccc"> -- )
>> CREATE ," IMMEDIATE  DOES> COUNT EVALUATE ;
>> 
>> When I first added this word to my Forth project I belived it would
>> allow me to define words that were 'macro expanded' in a text
>> substitution manner.
> 
> In some sense, which is why it is a bad idea.
> 
>> Is this indead the case ? The call to EVALUATE made me think this would
>> act as if it was text substitution rather than just a IMMIDEATE word
>> that would execute during compilation.
> 
> It's an immediate word that executes during compilation, so the text
> substitution part happens during compilation.  Leave away the
> IMMEDIATE and you get a word where the text substitution happens at
> run-time.  That is (for both), in the usual case.  When you tick or
> POSTPONE the word, you get something STATE-dependend (because the text
> interpreter used by EVALUIATE is STATE-dependend), and the behaviour
> you intended will probably only happen in one of the two states.
> 
> There are also other dependencies in this kind of word: dependence on
> BASE, on the search order, on the words in the wordlists on the search
> order, and other global state.
> 
> It's very easy to write buggy programs with these kinds of words, and
> hard to test for that stuff, so I call this concept bugros.
> 
> As an illustration of one of the dangers:
> 
> decimal
> macro ten 10 "
> 
> hex
> : foo ten ;
> decimal
> 
> foo .
> 
>> My intention was somthing that
>> would be expanded during compilation and therefore may get optimised as
>> inlined code into the word curently deing defined, so no subroutine
>> call overhead.
> 
> If you want optimization, get an optimizing compiler and write colon
> defintions.  The compiler will inline the colon definitions by itself.
> You will get better performance and fewer bugs.
> 
> - anton

OK, I'm convinced this MACRO word does more harm that good.

I don't agree that I should have to have an optimizing compiler to 
produce good code ! For my specific example about surface to surface 
blit routines, it's perfectly possible to do them without an optimizing 
compiler provided you have a good technique for source generation.

I'm only asking for somthing that I could achive in a macro assembler, 
I wouldn't have thought that was asking too much of Forth.

I guess the best way to go on this is to write an IMMEDIATE word that 
compiles the inner loop of the blit directly, takes the surface types 
as compile time paramaters and just places the code in the dictionary 
directly.

Chris

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macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 14:43 +0100
  Re: macro expansion ? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-06-28 10:58 -0500
    Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 18:34 +0100
      Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 18:51 +0100
        Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 19:02 +0100
          Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 19:11 +0100
            Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 19:17 +0100
              Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 19:47 +0100
                Re: macro expansion ? Josh Grams <josh@qualdan.com> - 2011-06-29 15:34 +0000
                Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-29 19:21 +0100
            Re: macro expansion ? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-06-29 03:15 -0500
              Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-29 13:11 +0100
            Re: macro expansion ? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-06-29 17:17 +0100
              Re: macro expansion ? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-06-29 18:09 +0100
                Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-29 19:32 +0100
                Re: macro expansion ? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-07-02 08:48 +0100
    Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-29 00:44 +0100
    Re: macro expansion ? Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2011-06-29 20:39 +0100
  Re: macro expansion ? Elizabeth D Rather <erather@forth.com> - 2011-06-28 08:59 -1000
    Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 20:39 +0100
      Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-28 21:34 +0100
        Re: macro expansion ? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2011-06-29 03:26 -0500
  Re: macro expansion ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-06-29 11:25 +0000
    Re: macro expansion ? Chris Hinsley <chris.hinsley@gmail.com> - 2011-06-29 13:24 +0100
      Re: macro expansion ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-07-03 14:02 +0000
    Re: macro expansion ? Albert van der Horst <albert@spenarnc.xs4all.nl> - 2011-06-29 18:48 +0000
  Re: macro expansion ? BruceMcF <agila61@netscape.net> - 2011-06-30 11:11 -0700
  Re: macro expansion ? Ian Osgood <iano@quirkster.com> - 2011-07-02 16:22 -0700
  Re: macro expansion ? Hugh Aguilar <hughaguilar96@yahoo.com> - 2011-07-05 17:35 -0700

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