Chuck McManis wrote: > This is a misuse of the term 'non-linear'. A non-linear weather system would > go from extremely hot, to snowing, instantaneously. That would constitute a > non-linear change in temperature. Complex certainly, but also just as certainly > a linear system. I think you're confusing "non-linear" with "discontinuous". A non-linear function is one which graphically is not a straight line. A discontinuous function is one where there "steps" or "breaks" in the transform, e.g. the tangent function is non-linear for any value, but discontinuous only at theta=pi. It also happens to be undefined for that value, but that's another issue. A discontinuous function must be, by definition, non-linear, but the reverse is not true. However, I'm not sure that Walter's description of the environmental control system as a "non-linear" system is particularly useful. There are very few problems in the real-world that are linear! It may be that the conflicting goals inherent in that system are the factor that makes it suitable for fuzzy logic (this would fit with many of the other mentioned applications, too). Clyde -- Clyde Smith-Stubbs | HI-TECH Software, | Voice: +61 7 3354 2411 clyde@hitech.com.au | P.O. Box 103, Alderley, | Fax: +61 7 3354 2422 http://www.hitech.com.au | QLD, 4051, AUSTRALIA. | --------------------------------------------------------------------------- For info on the World's best C cross compilers for embedded systems, point your WWW browser at http://www.hitech.com.au, or email info@hitech.com.au