It was rather specific when I wanted to reverse all ranks: I was trying to construct 3 dimensional curves. Further details I do not remember after almost 2.5 years.
I second your proposal for ;.0 although I estimate the chance of implementation is far less than epsilon. "Reversing y along each axis" seems to me as arbitrary as "trimming y along each axis" or "padding y with 0 along each axis" or any other operation on y "along each axis". R.E. Boss > -----Oorspronkelijk bericht----- > Van: [EMAIL PROTECTED] [mailto:programming- > [EMAIL PROTECTED] Namens Dan Bron > Verzonden: vrijdag 20 juni 2008 23:16 > Aan: Programming forum > Onderwerp: RE: [Jprogramming] Apply to all axis > > RE Boss asked: > > why "reversing y along each axis" was > > introduced in defining ;.0 > > My quick search didn't turn up a rationale, but in response to your (RE > Boss') "Reversing all ranks" thread, which I linked to earlier, Roger had > this to say: > > Ken told me that sometimes, when he came up with a neat > solution to a problem, he'd be accused of putting in > a special construct in the language just for that problem. > (And that was why the solution was so neat.) But the > accusation lost its sting when it was repeated in problem > after problem, in multiple diverse fields. > > (From http://www.jsoftware.com/pipermail/programming/2005- > December/000322.html ) > > As I read it, it was posted more-or-less in defense of the definition of > ;.0 , so maybe Ken saw this (reversing all ranks) as a recurring problem. > Roger, can you shed any light? > > Actually, RE Boss, maybe you can. You started that thread by asking for a > replacement for |."3@:(|."2)@:(|."1) . Do you remember why you wanted > to do that? I personally have not seen this problem recur in field after > field. > > In fact, after some research earlier today, it seems the recurring "all > ranks" problem is in fact the one that started this thread: padding an > array on all dimensions. Trimming (the opposite of padding) an array on > all dimensions came in second. > > -Dan > > PS: I don't remember ever wanting to "reverse all ranks", but I have > wanted an "alternating reversal" sometimes. That is, I wanted to reverse > every other item of an array. One of my prouder J moments was discovering > (A."_1~ _2 | i.@:#) for this purpose. There are other ways, too: > > http://www.jsoftware.com/pipermail/programming/2006- > November/004198.html > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
