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
