Thank you all for the explanation, clarification, and pointers. Highly appreciated. This list is great!!!
On Thu, Jul 11, 2013 at 12:26 PM, Roger Hui <[email protected]>wrote: > *./ .= is one of the earliest phrases given "special code" treatment in > APL. However, the use of *./ .= in J is much reduced compared to APL > because the computation is more conveniently done with extended i., > extended from the point of view of APL. Moreover: > > a=: a.{~97+1000 15 ?@$ 26 > x=: a{~ 1000 ?@$ 1000 > y=: a{~ 1200 ?@$ 1000 > (x *./ .=|: y) -: (x i. x) =/ x i. y > 1 > 10 timer 'x *./ .= |:y' > 0.0543126 > 10 timer '(x i. x) =/ x i. y' > 0.0069082 > > The comparison is nearly the same even if you exclude the time required for > the transpose |: > > ty=: |: y > 10 timer 'x *./ .= ty' > 0.05343 > > > > > > > On Thu, Jul 11, 2013 at 8:25 AM, Devon McCormick <[email protected]> > wrote: > > > You can use the dot to combine other things though it's probably most > > commonly used for matrix multiplication but it's a generalization of the > > ideas underlying that: > > > > >;:'This is a table of words' > > This > > is > > a > > table > > of > > words > > (>;:'This is a table of words') *./ . = 'table' > > 0 0 0 1 0 0 > > $>;:'This is a table of words' > > 6 5 > > (>;:'This is a table of words') *./ . = 5{.'of' > > 0 0 0 0 1 0 > > (>;:'This is a table of words') *./ . = |:>'of';'table';'FOO' > > 0 0 0 > > 0 0 0 > > 0 0 0 > > 0 1 0 > > 1 0 0 > > 0 0 0 > > > > And, of course, we also can extend matrix multiplication to higher > > dimensions: > > > > (i.2 3 4) +/ . * i.4 > > 14 38 62 > > 86 110 134 > > > > (i.2 3 4) +/ . * i.4 5 > > 70 76 82 88 94 > > 190 212 234 256 278 > > 310 348 386 424 462 > > > > 430 484 538 592 646 > > 550 620 690 760 830 > > 670 756 842 928 1014 > > > > > > > > On Thu, Jul 11, 2013 at 8:53 AM, Simon Barker <[email protected] > > >wrote: > > > > > J's parsing shows symbol recognition nicely: > > > > > > .* > > > +-+-+ > > > |.|*| > > > +-+-+ > > > *. > > > +--+ > > > |*.| > > > +--+ > > > . * > > > +-+-+ > > > |.|*| > > > +-+-+ > > > * . > > > +-+-+ > > > |*|.| > > > +-+-+ > > > > > > Searching archives by keyword: > > > > > > http://jsoftware.2058.n7.nabble.com/ > > > > > > As described here: > > > > > > http://www.jsoftware.com/jwiki/System/Forums > > > > > > Simon > > > > > > -----Original Message----- > > > From: [email protected] > > > [mailto:[email protected]] On Behalf Of Brian > > > Schott > > > Sent: 11 July 2013 13:38 > > > To: [email protected] > > > Subject: Re: [Jprogramming] What is .*? > > > > > > (B0 13) +/ .* (i.!]) 13x > > > I believe the code you are referring to is above. The phrase you are > > > looking > > > for is part of matrix multiplication. The dot is a separate symbol. > > > --- > > > (B=) > > > > > > On Jul 10, 2013, at 11:27 PM, Vijay Lulla <[email protected]> > wrote: > > > > > > > Hi all, > > > > Forgive me if this has been answered somewhere else previously. > > > > > > > > I was reading the essay on Bernoulli Numbers ( > > > > http://www.jsoftware.com/jwiki/Essays/Bernoulli%20Numbers) and came > > > > across > > > > .* (in the third code example block). I don't know what it does and I > > > > couldn't find anything in either the vocabulary or parts of speech > > pages. > > > > Any explanations/pointers are highly appreciated. > > > > > > > > On a side note, how do I search list archives for particular keyword > > > > or topic? > > > > Thanks in advance, > > > > Vijay. > > > > > ---------------------------------------------------------------------- > > > > 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 > > > > > > > > > > > -- > > Devon McCormick, CFA > > ^me^ at acm. > > org is my > > preferred e-mail > > ---------------------------------------------------------------------- > > 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
