It's not raze that loses the structure. raze makes a list of items: all structure in the ITEMS is preserved.
The problem is that when a list of boxes goes empty, the structure inside the boxes is lost. When you have < 2 5 $ 6 the box contains a table. If you have a list of such boxes, each holds a table. If you use ; on such a boxed list, the structure of the contents will be revealed. But when you have a 0-length array of such things, they are no longer (a list of 0) boxes containing tables, but (a list of 0) boxes containing empty lists. You could imagine having empty lists contain structure, but apparently APL variants tried that and the results were bad. The bottom line: when you have boxes containing tables, you must treat the empty-list-of-boxes as a special case. Henry Rich > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Don Guinn > Sent: Saturday, June 28, 2008 11:16 PM > To: Programming forum > Subject: Re: [Jprogramming] Extra empty item from an empty table > > What trapped me was that I used > > $0#i.1 2 > 0 2 > > quite a lot and it keeps structure. But raze does not. Thanks. > > 2008/6/28 Henry Rich <[EMAIL PROTECTED]>: > > > The problem is that you have a box containing structure > > (rank-2 arrays). When you raze them, you keep some of that > structure. > > But when you have 0 of the boxes, you lose the internal structure; > > the boxed empty is always treated like the contents are 0$0 . > > > > ;(<2 2$;:'abc de fg h'),<0#,:;:'ww xxxx' > > > > is equivalent to > > > > (2 2$;:'abc de fg h'),0#,:;:'ww xxxx' > > > > > > Note the subtle difference in boxing between this and your > first failing > > case. > > > > Henry Rich > > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] > > > [mailto:[EMAIL PROTECTED] On Behalf Of Don Guinn > > > Sent: Saturday, June 28, 2008 9:46 PM > > > To: Programming forum > > > Subject: Re: [Jprogramming] Extra empty item from an empty table > > > > > > Thank you for your comments. After reading the dictionary > on Raze (;) > > > several times I see why it didn't work. However, after > > > fooling around some > > > more I found what did work as I wanted. Need to spend a > > > little time really > > > understanding it. > > > > > > ;(<2 2$;:'abc de fg h'),<1#,:;:'ww xxxx' > > > +---+----+ > > > |abc|de | > > > +---+----+ > > > |fg |h | > > > +---+----+ > > > |ww |xxxx| > > > +---+----+ > > > ;(<2 2$;:'abc de fg h'),<0#,:;:'ww xxxx' > > > +---+--+ > > > |abc|de| > > > +---+--+ > > > |fg |h | > > > +---+--+ > > > > > > > > > On Sat, Jun 28, 2008 at 4:37 PM, Fraser Jackson > > > <[EMAIL PROTECTED]> > > > wrote: > > > > > > > > The following may be a simpler example of your problem. > > > > > > > > (2 2$;:'abc de fg h'),0$1 2 $a: > > > > ----T--┐ > > > > │abc│de│ > > > > +---+--+ > > > > │fg │h │ > > > > L---+--- > > > > (2 2$;:'abc de fg h'),0 2$a: > > > > ----T--┐ > > > > │abc│de│ > > > > +---+--+ > > > > │fg │h │ > > > > L---+--- > > > > (2 2$;:'abc de fg h'),0$a: > > > > ----T--┐ > > > > │abc│de│ > > > > +---+--+ > > > > │fg │h │ > > > > +---+--+ > > > > │ │ │ > > > > L---+--- > > > > > > > > > > > > ----- Original Message ----- From: "Don Guinn" > <[EMAIL PROTECTED]> > > > > To: "Programming forum" <[email protected]> > > > > Sent: Sunday, June 29, 2008 9:20 AM > > > > Subject: [Jprogramming] Extra empty item from an empty table > > > > > > > > > > > >> Was doing some recursive directory searches and needed to > > > combine the > > > >> results from multiple directories but when a directory did > > > not find any > > > >> items I got an item of nulls. Looking at the example shown > > > below, I don't > > > >> think I should get the item of nulls. > > > >> > > > >> (2 2$;:'abc de fg h'),;2#<,:;:'ww xxxx' > > > >> +---+----+ > > > >> |abc|de | > > > >> +---+----+ > > > >> |fg |h | > > > >> +---+----+ > > > >> |ww |xxxx| > > > >> +---+----+ > > > >> |ww |xxxx| > > > >> +---+----+ > > > >> (2 2$;:'abc de fg h'),;1#<,:;:'ww xxxx' > > > >> +---+----+ > > > >> |abc|de | > > > >> +---+----+ > > > >> |fg |h | > > > >> +---+----+ > > > >> |ww |xxxx| > > > >> +---+----+ > > > >> (2 2$;:'abc de fg h'),;0#<,:;:'ww xxxx' > > > >> +---+--+ > > > >> |abc|de| > > > >> +---+--+ > > > >> |fg |h | > > > >> +---+--+ > > > >> | | | > > > >> +---+--+ > > > >> > > > >> Why is there a third item which is empty in the last case? Am I > > > >> misunderstanding something about append? > > > >> > > > > ---------------------------------------------------------------------- > > > >> 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 > > > > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
