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<TITLE>RE: [movitz-devel] Self-referential functions</TITLE>
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<P><FONT SIZE=2>Ahh! I saw the definitions of things like cons and cdr and car that<BR>
were defined using the assembly macros, and I understood those. I sort<BR>
of understood the defmacro macro. The piece I was missing was that the<BR>
first compiler *directly* translated certain operators, like eq. But<BR>
wait, doesn't it do the same for car? Why do you need an assembly<BR>
definition of car and cdr but not eq?<BR>
<BR>
Ugh. Let my try to sort this out. Movitz has facilities for directly<BR>
manipulating bits and bytes (binary-types package). Upon these, it<BR>
builds facilities for translating x86 assembly into the binary opcodes<BR>
(ia-x86 package). It defines basic operators in terms of these. But it<BR>
doesn't need to define eq in binary?<BR>
<BR>
Oh, wait it does. I was just looking in the wrong place. In<BR>
movitz/losp/muerte/basic-macros.lisp, eq is defined as a compiler<BR>
macro. It's just that its defun is in equalp.lisp. Ha!<BR>
<BR>
So everything is defined, in the first compiler's lisp, down to the bit<BR>
and byte level. In movitz/image.lisp, there resides code to make a<BR>
binary bootable image out of all this. Its job is basically to expand<BR>
the lisp code into assembly and then into binary machine language. Once<BR>
this expansion is performed, you have defined the second, bootable,<BR>
lisp.<BR>
<BR>
I think I'm getting this, but please someone correct me if I got<BR>
something backwards.<BR>
<BR>
Chris Capel<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: Nyef [<A HREF="mailto:nyef@softhome.net">mailto:nyef@softhome.net</A>]<BR>
Sent: Thu 3/18/2004 8:31 PM<BR>
To: Chris Capel<BR>
Cc: movitz-devel@common-lisp.net<BR>
Subject: Re: [movitz-devel] Self-referential functions<BR>
<BR>
The compiler knows how to open-code the function eq, that is,<BR>
it will turn a reference to eq into the equivalent machine code<BR>
inline. But you still need the function object to exist so that<BR>
it can be funcalled, grabbed with symbol-function, function,<BR>
etc. So what the definition does is tell the compiler to make a<BR>
function object, called eq, that performs the eq operation. RPG<BR>
mentions this same thing in Patterns Of Software about the Lisp<BR>
implementation that his company wrote.<BR>
<BR>
--Alastair Bridgewater<BR>
<BR>
<BR>
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