Note that the grammar of this up-arrow operator conflicts with J's grammar.
So you'll need at least one other word in a J sentence that deals with this. Also, 'u' is a name that probably should be reserved for explicit adverbs and conjunctions (unless you know how J treats something named u different from most other names and you are ok with dealing with your audience in the context of those issues). In other words probably either: knuth 2 up up up up 3 or 2 knuth up up up up 3 That said, if you are willing to use actual numbers to distinguish between these up counts, that additional word becomes a number, and you could do it like this 2 (4 up) 3 (And you could skip the parenthesis if either the 2 or the 4 was represented by a name rather than a value.) Then again, if you didn't care about vector arguments (Knuth apparently didn't), you could do it like up 2 4 3 or any of a variety of other arrangements... FYI, -- Raul On Tue, Sep 18, 2018 at 2:40 AM Skip Cave <[email protected]> wrote: > > How would a J programmer build a verb that would emulate Knuth's up-arrow > notation <https://goo.gl/7pCZKW>? (https://goo.gl/7pCZKW). Tacit & explicit > versions would be nice. > > Examples - assuming the verb 'u' is the up-arrow: > > 2 u 4 = 16 > 2 u u 4 = 65536 > 2 u u u 3 = 65536 > 3 u u 2 = 27 > 3 u u 3 = 7,625,597,484,987 > > Skip > > Skip Cave > Cave Consulting LLC > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
