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From: "Rod Pemberton" <dont_use_email@xnothavet.cqm>
Newsgroups: comp.lang.forth
Subject: Re: Creating a lisp compiler
Date: Tue, 08 Apr 2014 06:04:42 -0400
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On Tue, 08 Apr 2014 03:16:38 -0400, Hi-tech Robert  
<hitechrobert@gmail.com> wrote:

> Hi, I am planning an OS for a Google glass-like hobby project I
> am working on.

...

> I am hoping to use Forth to create an assembler for lisp and
> Haskell.

Generally, assemblers are coded in assembly, or they're coded in the
language they're for, i.e., in lisp for lisp.  You're asking how to
produce a cross assembler.  Thoae are far less common.  In Forth
terminology, a cross compiler is called a meta-compiler.  So, I'm
assuming a cross assembler is called a meta-assembler.

> I am new to this language so please forgive my ignorance, any
> advice how?

Assemblers can be complicated, or not.  It depends heavily on the
assembly language for the specific microprocessor in question.
E.g., the x86 instruction set has some complicated encodings.

The rudimentary concepts are you parse syntax which tells you which
instruction to assemble and how the instruction format for that specific
instruction is to be filled in.  The information that needs to be
filled in can be a variety of things, such as offsets, bits to select
a register or memory location, etc.  This requires a bunch of bit
fiddling, with AND OR XOR etc.  The microprocessor instruction
manual for the microprocessor in question should show you the format
for each instruction.  Generally, Forth programmers concoct their
own syntax for a specific assembly language, whereas other coders
will use the syntax provided by the microprocessor instruction manual.
This is because Forth's have a limited but functional parser built into
the language.

As for using the Forth language to do this, others here will have to
help you.


Rod Pemberton