Listed under "Requests" here: https://code.jsoftware.com/wiki/System/Interpreter/Requests#Support_inverse_for_I._y
Forum discussions: http://www.jsoftware.com/pipermail/general/2006-April/026874.html http://www.jsoftware.com/pipermail/programming/2010-September/020281.html http://www.jsoftware.com/pipermail/programming/2017-June/047737.html Marshall On Wed, Oct 02, 2019 at 12:50:07PM -0400, Michal Wallace wrote: > Does I.inv have a working implementation? > > I'd expect the domain to be any ascending sequence of positive whole > numbers (possibly with repeats): > > 3 4 9 e.~ i.10 > 0 0 0 1 1 0 0 0 0 1 > I. 3 4 9 e.~ i.10 > 3 4 9 > I. (i.@:>:@(>./) e. ]) 3 4 9 NB. hypothetical I.inv, doesn't handle > repeats > 3 4 9 > > But anything I throw at it gives me a domain error: > > I.inv 3 4 9 > |domain error > | I.inv 3 4 9 > > > What am I missing? > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
