Thanks Roger! On https://en.wikipedia.org/wiki/Talk:Exponentiation 0^0 is discussed. I need all the help I can get. Your information is very welcome. Thank you! Bo.
Den 21:30 fredag den 17. januar 2014 skrev Roger Hui <rogerhui.can...@gmail.com>: BTW, Knuth did something else which typifies APL thinking. In a note or >paper (I can not find it now), he argued strongly that 1=0^0, not >undefined, not 0, not anything else. The common conventional statement of >a polynomial, p(x)=sigma(k=0;k<=n) a[k]*x^k, requires that x^0 be 1. Some >writers are aware of this dependency and, being careful, write instead the >ugly p(x)=a[0]+sigma(k=1;k<=n)a[k]*x^k. > >Attention to edge cases is typical of APL thinking. It's another way to >stay in the world of expressions and away from the world of statements. >You know: > >if k=0 then >a[0] >else >a[k]*x^k >endif > > > > > >On Wed, Jan 15, 2014 at 6:20 PM, Roger Hui <rogerhui.can...@gmail.com>wrote: > >> One aspect: J/APL programmers tend to stay in the nice world of >> expressions and avoid the nastier world of statements. This tendency >> pushes you towards array thinking and away from scalar thinking. >> >> For example, if b is a boolean array, and you want 4 where b is 0 and 17 >> where b is 1, write: >> >> (4*0=b)+(17*1=b) >> >> And of course the signs of real numbers x are: >> >> (x>0)-(x<0) >> >> Even Knuth, an eminent mathematician and computer scientist but not an APL >> programmer, knows to <strike>steal</strike> adopt this idea. See: Knuth, >> *Two >> Notes on Notation* <http://arxiv.org/PS_cache/math/pdf/9205/9205211v1.pdf>, >> 1992-05-01. In the first half of the paper he describes how "Iverson's >> convention" can be used to simplify the statement and manipulation of sums. >> >> See also: >> >> http://www.jsoftware.com/papers/perlis77.htm >> http://www.jsoftware.com/papers/perlis78.htm >> http://www.jsoftware.com/papers/APLQA.htm#Perlis-foreword >> >> >> >> >> >> On Wed, Jan 15, 2014 at 5:32 PM, Joe Bogner <joebog...@gmail.com> wrote: >> >>> I went googling for some deeper material on how to think like an APL >>> programmer. I have read/skimmed through a good set of the material on >>> http://jsoftware.com/papers/ and have skimmed through many of the >>> books listed on http://www.jsoftware.com/jwiki/Books. >>> >>> Are there any specific recommendations, free or for purchase? Or, >>> perhaps I should spend more time with the list above. >>> >>> I found this, The APL Idiom List by Perlis and Rugaber, which looks >>> similar to what I'm looking for: >>> http://archive.vector.org.uk/resource/yaleidioms.pdf. >>> >>> The review of this book looks like what I'm after, >>> >>> http://www.amazon.com/Handbook-APL-programming-Clark-Wiedmann/dp/0884050262 >>> , >>> constructing useful programs and going into more depth. >>> >>> Or something of the style of The Little Schemer, >>> http://scottn.us/downloads/The_Little_Schemer.pdf >>> >>> I searched the forum and had trouble finding a relevant post >>> ---------------------------------------------------------------------- >>> For information about J forums see http://www.jsoftware.com/forums.htm >>> >> >> >---------------------------------------------------------------------- >For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
