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Re: gEDA-user: Google SoC : Potential Candidate seeking Info

al davis wrote:
> Another interesting type of analysis that Spice doesn't have is 
> a semi-symbolic analysis, where the result is a transfer 
> function, in S, that has some values carried through as 
> symbols.  I would have to help you a lot, but it would be a 
> real accomplishment, and I think I know of a few places where 
> you could get a paper out of it. .. at least a conference 
> paper, maybe two, maybe even a journal paper.


anyone remember the program xfunc which did exactly this?  I have tried 
to track down the author a few times over the years with no luck.

The manual says:

XFUNC 1.2
Transfer Function Symbolic Calculator

Copyright 1991 - YY Corporation


The program was distributed with sources and a DOS binary.  The 
programmer is listed as Henry Yiu.  History shows 1989 as the original 
release date and 1991 as the most recent.  I do not see any sort of 
license anywhere.  Just the copyright notice.

The tool worked and really my primary complaint was that you quickly 
ended up with an expression that

a) was not at all a low entropy expression (see various papers by 
Middlebrook or the textbook by Vorperian)

b) represented polynomials as the coefficients like
   1 + a1*s + a2*s^2 + a3*s^3 ....

which of course tends to be a poor way to represent polynomials from 
both a numerical sense and an insight sense.

That said, it was still useful from time to time.

If anyone would have a clue on how to contact Henry Yiu it might be 
interesting to see if he would provide a license that allows for 
redistribution.  GPL would work.  The program is in C and doesn't take 
much to build on modern systems.  If he were willing, I'd volunteer to 
get it into a version control system (probably git) and provide a build 
system other than the DOS build system.

-Dan

-Dan


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