[Reduce-algebra-developers] misprint in "Computer Algebra with LISP and REDUCE"? From: Spencer Cathey - 2013-10-23 05:08:43 Attachments: Message as HTML ```Newbie question. Perhaps someone familiar with this book could explain what I am not understanding... near bottom of p. 227 else if not vectorp(action(x, ! x)) then the trouble is, '! x', which I presume is the escape character preceding a literal, makes no sense in the context of the code, unless, of course, I have missed something. There's another ! in procedure whatline on p.235, that again makes no sense as the usual character literal escape sequence. Is there another interpretation I do not know? Anyways, regardless if anyone could assist me, having the answer off the top of their head, saving me a little time, I felt that with the increasing interest in Geometric Algebra and REDUCE, and with the number of people learning these topics in self-study, it would not hurt to mention what I feel is a fine chapter in a fine book. Thank you, S. Cathey Computer Algebra with LISP and REDUCE F. BRACKX and D. CONSTALES ```
 [Reduce-algebra-developers] misprint in "Computer Algebra with LISP and REDUCE"? From: Spencer Cathey - 2013-10-23 05:08:43 Attachments: Message as HTML ```Newbie question. Perhaps someone familiar with this book could explain what I am not understanding... near bottom of p. 227 else if not vectorp(action(x, ! x)) then the trouble is, '! x', which I presume is the escape character preceding a literal, makes no sense in the context of the code, unless, of course, I have missed something. There's another ! in procedure whatline on p.235, that again makes no sense as the usual character literal escape sequence. Is there another interpretation I do not know? Anyways, regardless if anyone could assist me, having the answer off the top of their head, saving me a little time, I felt that with the increasing interest in Geometric Algebra and REDUCE, and with the number of people learning these topics in self-study, it would not hurt to mention what I feel is a fine chapter in a fine book. Thank you, S. Cathey Computer Algebra with LISP and REDUCE F. BRACKX and D. CONSTALES ```
 Re: [Reduce-algebra-developers] misprint in "Computer Algebra with LISP and REDUCE"? From: René Grognard - 2013-10-23 07:16:07 Attachments: Message as HTML ```I no longer have access to a copy of that book but I think that the code comes anyway from the Clifford packages which were more than 13 years ago still freely available from Ghent Uni. I translated them for maxima as basis for my own work on Clifford Analysis after retiring and losing thereby access to Reduce. A couple of years ago I retranslated my code in Reduce when the latter became free software. Here is I believe the relevant code: % SOME SPECIAL CLIFFORDS ! x:= x_1*e(1)+ x_2*e(2)+ x_3*e(3); procedure action(a,b); bar(a)*b*a; The reason for introducing strange identifiers with a space as first character (whence the necessity of the prefix !) such as ! x is simply to prevent the user to redefine them! So action(x,! x) simply calculates bar(x)*( x_1*e(1)+ x_2*e(2)+ x_3*e(3))*x. I guess that other case you mention is again a predefined constant Clifford expression with identifier starting with a space. René Grognard. bar(a)*b*a; On Wed, Oct 23, 2013 at 4:08 PM, Spencer Cathey wrote: > Newbie question. > Perhaps someone familiar with this book could explain what I am not > understanding... > near bottom of p. 227 > > else if not vectorp(action(x, ! x)) then > > the trouble is, '! x', which I presume is the escape character preceding a > literal, > makes no sense in the context of the code, unless, of course, I have > missed something. > There's another ! in procedure whatline on p.235, that again makes no > sense as the usual > character literal escape sequence. > > Is there another interpretation I do not know? > > Anyways, regardless if anyone could assist me, having the answer off the > top of their head, > saving me a little time, I felt that with the increasing interest in > Geometric Algebra and REDUCE, > and with the number of people learning these topics in self-study, it > would not hurt to mention what > I feel is a fine chapter in a fine book. > Thank you, > S. Cathey > > > Computer Algebra with LISP and REDUCE > F. BRACKX and D. CONSTALES > > > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most > from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60135991&iu=/4140/ostg.clktrk > _______________________________________________ > Reduce-algebra-developers mailing list > Reduce-algebra-developers@... > https://lists.sourceforge.net/lists/listinfo/reduce-algebra-developers > > ```