Re: What's the spec for emacs lisp virtual machine ?

[Fren Zeee]

On Jul 23, 1:34 am, p...@informatimago.com (Pascal J. Bourguignon)
wrote:
> Fren Zeee <frenz...@gmail.com> writes:
> > What's the spec for emacs lisp virtual machine ?
>
> The source code of emacs.
>
> > Where are the complete set of virtual machine commands ?
>
> In src/bytecode.c
>
> > Where is the theory for such a virtual machine in the clearest
> > description ? (not general theory, but one applicable directly to
> > understanding emacs vm.)
>
> It's really quite a simple VM.  Just read the sources!
>
> > Does the emacs lisp operate as a stack push/pop or as parsing ?
>
> emacs lisp works like any other lisp.  There's an abstract 'eval' that
> interprets it.  Any good course about lisp would introduce it.
>
> > Why is a VM needed when there is compiled C code running machine
> > code ?
>
> Is this home work?
>
> Search the sources of emacs for compilers.
> How many compilers do you find?
> What are their source files?
> What machine do they target?
>
> > How do you implement a LISP interpreter using a stack based and syntax
> > tree methods ?
>
> Interpretation may be done without any consideration on the underlying
> architecture.
>
> > Some overview with concrete examples please, but of practical value.
>
> Perhaps you should not limit yourself to emacs lisp.  Allow yourself
> to read also about other lisps, including scheme.  
>
> You could also check the sources of various other Lisp, including:
> - sbcl or ccl,
> - clisp, and
> - ecl
> to answer the above questions for them as well as for emacs lisp.
>
> There's a lot of material out there.  You could start with:
>
>  http://www.informatimago.com/develop/lisp/small-cl-pgms/aim-8/
>    (that paper contains the original LISP interpreter).
>
> Googling for: lisp in lisp
> gives good results such as:
>
>  http://lib.store.yahoo.net/lib/paulgraham/jmc.lisp
>
>  http://www.softwarepreservation.org/projects/LISP/
>
>  http://www.schemers.org/Documents/Standards/R5RS/HTML/r5rs.html
>    (this report contains (part of) formal specifications of scheme).
>
> > Also, for either you need a scanner and so an example of a scanner
> > using a transition table. How do you decide on the states that are
> > minimal and not redundant ?
>
> > What is the difference between a stack architecture of a processor and
> > register based one ?
>
> Get a description of a stack architecture.
> Get a description of a register based processor.
> Compute the differences.
>
> If you're lazy, as it seems you are, you could just
> use google:  stack vs register VM
>
> > wouldnt the former still need an ALU and indirect
> > addressing to do the job ?
>
> What do you think?
>
> > A diagram and some explanation, or else we
> > will be in the domain of linguistic ambiguity.
>
> Or even better, use formal specifications for the various kind of VM,
> and a formal specification of Lisp, and show how you can map the later
> to each one of the formers.
>
> > Upload a hand sketched image if necessary, or a reference to specific
> > pages in google books.
>
> > I have done searches on wiki and other places but the things are not
> > entirely clear because they are not oriented to my goal of centering
> > around emacs.
>
> You need to read LiSP, which covers how to implement Lisp.
>
> LiSP   = "Lisp in Small Pieces"  
>          http://www-spi.lip6.fr/~queinnec/WWW/LiSP.html
>          This book covers Lisp, Scheme and other related dialects,
>          their interpretation, semantics and compilation. To sum it up
>          in a few figures: 500 pages, 11 chapters, 11 interpreters and
>          2 compilers.
>
> --
> __Pascal Bourguignon__                    http://www.informatimago.com/

unfortunately, this reply did not give any benefit and info repeated
before. the reply did not even put a snippet of the code from c file
to illustrate how he himself read and understood it. someone else try
if anyone knows.