It is not a bug and the following sequence illustrates why the behavior is reasonable:
(n$0) , i. 2 2 [ n=: 3 0 0 0 0 1 0 2 3 0 (n$0) , i. 2 2 [ n=: 2 0 0 0 1 2 3 (n$0) , i. 2 2 [ n=: 1 0 0 0 1 2 3 (n$0) , i. 2 2 [ n=: 0 0 0 0 1 2 3 On Fri, Jan 11, 2013 at 8:52 AM, Steven Taylor <tayl...@gmail.com> wrote: > I didn't expect this extra (0 0) in the result. > > (0 $ 0),i. 2 2 > 0 0 > 0 1 > 2 3 > > i.e. nothing prepended to shape equals the same shape (not more or less) > > Is this a bug, or does this make sense in some situations? What should the > J way be? > > For a simple list, we get my expected behaviour : > > (0 $ 0),i. 3 > 0 1 2 > > Here's a possible solution > > empty=:(<'') = [: < [ > > empty 0 $ 0 > NB. build result > (xci sort~ u,xa),ya > ) > > empty=:(<'') = [: < [ > > carefulappend=:13 : '(empty x)}. x,y' f. > > carefulappend2=:4 : 0 > if. (empty x) do. > r=.y > elseif. empty y do. > r=.x > elseif. do. > r=.x,y > end. > r > ) > > (0 $ 0) carefulappend i. 2 2 > 0 1 > 2 3 > > (0 $ 0) carefulappend2 i. 2 2 > 0 1 > 2 3 > > thanks, > -Steven > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
