rad=: 13 :'(A=:1,-. 2-:/\|:y)#"1 y' NB. Remove adjacent duplicates]B=:2 4 $3 5 5 4 2 1 1 6 3 5 5 4 2 1 1 6 rad B 3 5 4 2 1 6 The verb rad works as expected, but suppose in an earlier step B has become empty, I get a length error. Why does this happen? C=:'' rad C |length error: rad | (A=:1,-.2-:/\|:y) #"1 y A 1 1#"1 C What can I do to get an empty result? Linda ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
