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Groups > comp.lang.forth > #3612

Re: macro expansion ?

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On 2011-06-28 19:17:35 +0100, Chris Hinsley said:

> On 2011-06-28 19:11:15 +0100, Chris Hinsley said:
> 
>> On 2011-06-28 19:02:24 +0100, Chris Hinsley said:
>> 
>>> On 2011-06-28 18:51:51 +0100, Chris Hinsley said:
>>> 
>>>> On 2011-06-28 18:34:06 +0100, Chris Hinsley said:
>>>> 
>>>>>>> 
>>>>>>> But this led me on to thinking how would I do a more Lisp like macro ?
>>>>>>> Somthing that would be expanded and then that expantion expanded till
>>>>>>> there was no more expantions.
>>>>>> 
>>>>>> I think that's going to happen anyway.  When EVALUATE comes across a
>>>>>> MACRO it'll expand it recursively.
>>>>>> 
>>>>>> Perhaps you could show us an example of something like this not
>>>>>> working.
>>>>>> 
>>>>>> Andrew.
>>>>> 
>>>>> A simple example that does work as intended.
>>>>> 
>>>>> macro ma * +"
>>>>> macro mp1 1 -rot ma"
>>>>> : t1 1 -rot * + ;
>>>>> : t2 mp1 ;
>>>>> 
>>>>> Both t1 and t2 dissesemble to exactly the same code. Good that's as I 
>>>>> intended. And show the expansion of macros is recursive. :)
>>>>> 
>>>>> However now I'm thinking how would a do a macro that can use itself ? 
>>>>> Part of this is no problem, the EVALUATE call will be able to find the 
>>>>> named macro and recurse in no problem.
>>>>> 
>>>>> macro bert bert"
>>>>> 
>>>>> Would just recurse till it crashed. But there's no problem with defineing it.
>>>>> 
>>>>> So how would I exit a macro expansion ? I'd presumably have to have 
>>>>> interpret time, rather than runtime conditions used in the macro ?
>>>>> 
>>>>> Forgive me if I'm rambling a bit, I'm making this up on the fly here, 
>>>>> trying to see if I can spot a problem. Would I hit a problem that IF, 
>>>>> ELSE, ENDIF are only available as compile time words (well they are for 
>>>>> my Forth, I know others have made them work at interpret time). Maybe 
>>>>> you just stick to useing [IF], [ELSE], [THEN] in macro definitions and 
>>>>> it will all just work (tm).
>>>>> 
>>>>> I'll try a few more experiments.
>>>>> 
>>>>> Chris
>>>> 
>>>> OK, somthing definate as an example I'd like to see work.
>>>> 
>>>> Lets say I have a Forth Hakiu pixel shader, it defines a word that 
>>>> takes x,y and gives back an ARGB. Normally I call this each pixel at 
>>>> runtime to generate a pixel on the fly, either in a shader on the GPU 
>>>> or with a peice of code that creates a texture at runtime.
>>>> 
>>>> However, maybe I'd like to create a macro that uses the Haiku to create 
>>>> an embeded version of the texture as read only data stored as a word 
>>>> that returned a pointer to the embeded array of pixels ? All the 
>>>> processing of the pixels is to be done at compile time, no runtime 
>>>> overhead. Can I create a _macro_ that expands into the ARGB data array 
>>>> given a Hauku name and resolution value at compile time ?
>>>> 
>>>> I'm just throwing this out as an example, I've not actualy tried to do 
>>>> it yet, but it might show up a problem. I can see that you could define 
>>>> a word that is an IMMEDIATE word to do this job at compile time, but 
>>>> can you do it with the/a macro concept ?
>>>> 
>>>> Chris
>>> 
>>> How about a macro that did greatest common divider ?
>>> 
>>> Function gcd(a As Integer, b As Integer) As Integer
>>> If b = 0 Then
>>> gcd = a
>>> Else
>>> gcd = gcd(b,a)
>>> End If
>>> End Function
>>> 
>>> Chris
>> 
>> I think I'm rapidly getting into the 'but you wouldn't do it like that' 
>> teritory. You'd just define a word that did the calcutation, and then 
>> use it with somthing like [ 15 5 GCD ] LITERAL.
>> 
>> But I'm pushing the issue of how you'd do it with a macro called GCD to 
>> expose the limits.
>> 
>> Chris
> 
> Err I think that should be:
> 
>  gcd = gcd(b, a mod b)
> 
> Sombody was bound to point this out, so I'll fess up to getting it wrong now.
> 
> Chris

A big problem with doing recursive macros is that EVALUATE will push a 
potentially unknow amount of state on the stack before the next 
iteration of the macro ? I suppose you could create another stack for 
use within macros but it's all getting really horible.

Chris

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Thread

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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