I suspect that having [email protected] be for all programming issues should be classified as a kind of "pun"ishment.
Anyways, http://www.jsoftware.com/forums.htm says that the programming forum is for "the main forum, covering J programming from beginner to expert, and announcements" Perhaps those single line descriptions should be auto-appended to list emails? That would avert the current problem where people rarely see them. It's verbose, but so is top posting (which has been the favored response format on these lists). And, for better or worse, I put my detailed response into the chat forum. http://jsoftware.com/pipermail/chat/2013-January/005046.html is the errata. -- Raul On Mon, Jan 28, 2013 at 1:43 PM, Devon McCormick <[email protected]> wrote: > You can also do your "flip" step in much the same way, something like (in a > "j" rows (for half of them), "k" columns loop): > temp= b[j][k]; > b[j][k]= b[MAXROW-j][k]; > b[MAXROW-j][k]= temp; > > I think this thread should remain in programming even if it's C-oriented as > this is still, technically, programming. > > > On Mon, Jan 28, 2013 at 1:30 PM, Raul Miller <[email protected]> wrote: > >> The C approach to doing transpose typically involves swapping the >> indices when they are used, and not bothering to make a fresh copy (or >> updated copy) of the data. >> >> This of course yields a fair bit of complexity which gets pushed into >> the code (or into the objects) but that's how it's usually done. >> >> That said, you can achieve the same thing by explicitly copying the >> matrix using swapped indices. In a loop; b[j][k]= a[k][j] >> >> Or am I overlooking something important? >> >> (Also, perhaps this thread should be in chat?) >> >> Thanks, >> >> -- >> Raul >> >> On Mon, Jan 28, 2013 at 12:58 PM, Brian Schott <[email protected]> >> wrote: >> > I am trying to use objective C and am using j to develop some >> > pieces. I have the verb `transposeSquare` which transposes a square >> matrix's >> > indices using indices and reproduces j's Transpose. In C code the indices >> > are named ii and are being generated in a for loop as follows, where >> width >> > and height are actually both 13 but my j examples use 3 instead of 13. >> > >> > for (int ii = 0 ; ii < width * height ; ++ii) >> > >> > transposeSquare =: (] <.@% %:@#)+#| %:@# *] >> > transposeSquare i. 9 >> > 0 3 6 1 4 7 2 5 8 >> > ,|:i. 3 3 NB. this is the "J way" >> > 0 3 6 1 4 7 2 5 8 >> > >> > Now with C code for loop in mind I need a verb which first does >> what >> > transposeSquare does and then reverses the indices using the operators >> > available to C so that the result of the verb would be as follows. >> > >> > ,|.|:i. 3 3 NB. this is the "J way" >> > 2 5 8 1 4 7 0 3 6 >> > >> > That is, I need a verb (say, reverseOfTranspose, rOT), which >> gives >> > the same result as ,|.|:i. 3 3 but with the scalar argument 3 and is >> limited >> > to C operators. >> > >> > (B=) >> > ---------------------------------------------------------------------- >> > 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
