A couple of weeks ago, Richard W. M. Jones released JONESFORTH, which I thought was pretty exciting. Today I spent a few hours porting the assembly-language part to PowerPC on Mac OS X 10.3.9. It ended up being 600 non-comment lines of code in total, and took me about eleven hours in total to write and debug. It runs the standard JONESFORTH prelude, up to and including SEE.
You can download the code here: ppcforth.S.m4.
(It’s also available via darcs:
The assembler-macro tricks that the original i386 version uses are sadly unavailable with the default OS X assembler, so I’ve had to resort to using
instead; other than that, it’s more-or-less a direct translation of Richard’s original program. To compile it,
m4 ppcforth.S.m4 > ppcforth.S gcc -nostdlib -o ppcforth ppcforth.S rm ppcforth.S
To run it, download the JONESFORTH prelude (save it as
$ cat jonesforth.f - | ./ppcforth JONESFORTH VERSION 14641 OK
Here’s an example session, decompiling the “ELSE” word:
SEE ELSE : ELSE IMMEDIATE ' BRANCH , HERE @ 0 , SWAP DUP HERE @ SWAP - SWAP ! ;
I’d like to thank Richard for such an amazingly well-written program: not only is JONESFORTH itself a beautiful piece of software, it’s also an incredibly lucid essay that does a wonderful job of introducing the reader to the concepts and techniques involved in implementing a FORTH.