I think 13 : has already been mentioned in your previous thread as another useful tool when developing tacit expressions.
If you can write the expression explicitly, 13 : will translate it to tacit for you. For example: nPrX=: 4 : '(!y) * y!x' 14 nPrX 3 2184 13 : '(!y) * y!x' ([: ! ]) * !~ +--------+-+-----+ |+--+-+-+|*|+-+-+| ||[:|!|]|| ||!|~|| |+--+-+-+| |+-+-+| +--------+-+-----+ nPr=: ([: ! ]) * !~ 14 nPr 3 2184 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
