The "librep" virtual machine uses a technique taken from Forth engines called "indirect threading". That's not threading as in "multithreading" or "pthreads"... You'll have to read about it for yourselves, since I've not the knowledge, time, or the inclination to write a long essay on the subject. I can tell you "it exists" and show you where to find out about it, however.
When GCC is the compiler, "rep" uses the "address of label" and "computed goto" features to build a jump table into the interpreter/decoder "loop". So rather than test, fail, branch, test, fail, branch, ..., test, hit, execute, branch in a long switch statement, it uses the opcode as the index into a jump table, and does a "goto table[op]" instead. When it's built with some olde slowunuchs compiler, it falls back to being a switch statement, through fancy use of the CPP "macro" system. It's really very amazing and clever. >From <URL:http://www.geocrawler.com/archives/3/688/2001/3/0/5397900/>: @InProceedings{ertl93, author = "M. Anton Ertl", title = "A Portable {Forth} Engine", booktitle = "EuroFORTH '93 conference proceedings", year = "1993", address = "Mari\'ansk\'e L\'azn\`e (Marienbad)", url = "http://www.complang.tuwien.ac.at/papers/ertl93.ps.Z";, } Additionally, a search for this author, paper, and/or subject on CiteSeer may prove fruitful... (bookmark this one!) <URL:http://citeseer.nj.nec.com/> The "librep" byte code engine is very fast. Anyone who has used "sawfish" can attest to it's quickness. My guess is that a good look at librep (and some Rep Lisp code) might prove very interesting. Surely John Harper has already encountered many of the similar problems the Parrot developers are faced with! <URL:http://librep.sourceforge.net/> The list archives there are probably worth mining, so bring your reading headlamp when you visit the list mine under the source forge. I would really like to see Parrot able to run "rep" lisp/scheme and "guile" with "goops" also. Do you know about them? It's worth spending some time to research, IMHO, so put your googles on guile's goops! (and click on that headlamp in their mailing list archives also.) ... and I've heard that "rscheme" has a real time generational garbage collector of some kind. I wonder if it's readable enough to use as a guide, portable enough to rip out and install, or even worth the bother? (I'm not good enough at it to understand the thing yet.) [ I sail a coffee mug in the general direction of a wall... Bring us WATER, dag nab it. I want something _healthy_ to drink so my brain doesn't break. ] -- mailto: (Karl M. Hegbloom) [EMAIL PROTECTED] Free the Software http://www.debian.org/social_contract http://www.microsharp.com phone://USA/WA/360-260-2066
