Thank you R.E. Boss and Brian. The reference material is so good. Yes, I'm clearer on agreement now. And I'm not sure it's worth troubling you all with this, but my underlying problem was linked with the empty vector. What I was wanting was a verb c with these properties:
0 1 c 0 1 2 0 0 0 1 0 2 1 0 1 1 1 2 '' c 0 1 2 0 1 2 I was trying to build an array using c repeatedly with the same rh argument, beginning from an empty vector as the lh argument, but subsequently using the previous result. c=: ,"0/ does for all examples but the empty vector case. But looking into it, the second case is the odd one out since the shape of any result of c must always end in 2. My solution is to use one less iteration by missing out the first! But I am always eager to understand what's confusing me. Thanks for your help. Graham ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
