>wfdavis@davis-inc.com <wfdavis@davis-inc.com> wrote:
>
>> With all due respect, Gray-codes, also known as cyclic codes, are
>> defined as _any_ scheme for mapping the sequence of integers into
>> another representation in which successive members differ by one bit
>> in the representation.
>>
>> See Gray-code in, for example, The McGraw-Hill Dictionary of
>> Scientific and Technical Terms or Van Nostrand's Scientific
>> Encyclopedia.  They define Gray-code as "a" method, not "the"
>> method. More particularly, see: Digital Computer Systems Principles
>> by Herbert Hellerman, McGraw-Hill, p. 315 (1967).  In his section on
>> Encoding, Hellerman makes it explicitly clear that the reflected
>> code is but one of many codes that fall under the general definition
>> of a Gray-code.
>
>    Thanks for straightening this out, Warren... Like Ray, I was
>    under the mistaken impression that there was only one Gray code
>    for any sequence of integers.
>
>    My apologies to anyone who was misled by my ignorance.
>
>    -Andy
>
>=== Andrew Warren - fastfwd@ix.netcom.com                 ===
>=== Fast Forward Engineering - Vista, California          ===



I refuse to give up so easily :-)

Admittedly, the term "Gray code" has come to be applied fairly widely to all
"single distance codes". Whether or not this is correct or incorrect
is not really the question. The question that will arise in the
future is what happens when I buy a rotary encoder which claims to be
Gray code, what I get may or may not be The particular Gray code I am
expecting. ....the result is that for all practical purposes the term
Gray code ceases to have any value for determining how the system
software handles the encoder input. As does the phrase .."here is a neat
algorithm for converting Gray codes to binary"....to which we will all
answer, "and what particular single distance code might that be?"

I give up!  :-)

In the process of checking the literature I came across a few interesting
references. Might make good reading over Christmas.

http://www.cs.auckland.ac.nz/~techrep/TR131/doc.txt
A good collection of references, plus includes Frank Gray original
description from his patent. (symmetric of course)

Also interesting connection with Venn Diagrams can be found at.
http://sue.csc.uvic.ca/~cos/venn/VennSymmEJC.html


Thanks for an interesting thread,

                 Merry Christmas...





Ray Gardiner, Shepparton, Victoria, Australia:  ray@netspace.net.au