A few other interesting contextual tidbits. - The encounter was recorded in "A Source Book in APL". http://www.jsoftware.com/jwiki/Doc/A_Source_Book_in_APL The occasion was the Working Conference on Mechanical Language Structures, Princeton, NJ, August 14-16, 1963.
- The list of conferees included John Backus, Haskell Curry, Dijkstra, Robert Floyd, Sheila Greibach, Iverson, Alan Newell, Alan Perlis, Maurice Wilkes. 7 of these people later won the Turing Award. - Just before Dijkstra question, S. Gorn asked: Does your generalized operator notation for matrices lead to a simpler proof of the generalized Laplace expansion of determinants? Followed by Ken's answer of about 20 dense lines. If Ken did that on the fly in immediate response then it was a fantastic feat. The answer to Dijkstra's question was far far easier in comparison. ----- Original Message ----- From: Roger Hui <[EMAIL PROTECTED]> Date: Wednesday, November 7, 2007 18:10 Subject: Re: [Jchat] why did Dijkstra dislike APL so much? To: Chat forum <[email protected]> > I might say: > > +/ , M * M = +/&> {i.&.> $M > 6 > > If I were under pressure (e.g. with Dijkstra in the audience > asking the question) and wanted to avoid any fumbling, > I might say: > > +/ , M * M = (i.#M) +/ i.{:$M > 6 > > And then from that to successively "better" answers > +/ , M * M = (#M) +/&i. {:$M > +/ , M * M = +/&i./ $M > +/ , M * M = +/&> {i.&.> $M > not forgetting to point out that the last expression > works for M of any rank. > > Dijkstra's question in 1963 was: How would you represent a > more complex operation, for example, the sum of all elements of > a matrix which are equal to the sum of the corresponding row > and column indices? > > > > ----- Original Message ----- > From: Oleg Kobchenko <[EMAIL PROTECTED]> > Date: Wednesday, November 7, 2007 17:00 > Subject: Re: [Jchat] why did Dijkstra dislike APL so much? > To: Chat forum <[email protected]> > > > What is the standard J answer? > > > > ((= +/@#&, [) +/&i./@$) i.3 4 > > 6 > > (+/@#~&, (= +/&i./@$)) i.3 4 > > 6 > > (+/@,@:* (= +/&i./@$)) i.3 4 > > 6 > > +/,M*M=+/&i./$ M =. i.3 4 > > 6 > > > > > > --- Roger Hui <[EMAIL PROTECTED]> wrote: > > > > > I don't know of any and I suspect Ken was too smart to respond. > > > > > > There was an encounter between KEI and Dijkstra recorded in > > > http://keiapl.info/anec/#Dijkstra > > > > > > > > > > > > ----- Original Message ----- > > > From: Richard Hill <[EMAIL PROTECTED]> > > > Date: Wednesday, November 7, 2007 15:21 > > > Subject: Re: [Jchat] why did Dijkstra dislike APL so much? > > > To: Chat forum <[email protected]> > > > > > > > Is there any record, or even an anecdote, of KEI's > > > > own response to Dijkstra's comment? > > > > Richard Hill ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
