Reading the wonderful NuVoc I found the gem that dyadic # has an inverse - it can therefore be used in &. like
>: &. (0 0 1 0 0 1&#) i.6 0 0 3 0 0 6 , executing a function only on selected items of an array while keeping the shape. The bit array is a noun, but I want to compute it on the fly (from the right argument). If the v in u&.v had dyadic valence, something like 0 0 1 0 0 1 >:@] &. # i.6 would be possible and the left argument could be replaced by a computation. Here I'm stuck. From what I understood so far this seems to be impossible - the v in the &-conjunctions is always monadic. Is there a way to save the idea? P.S.: needed in AoC day 24... ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
