Hi Luca Here is a link to a previous forum thread on this topic: http://www.jsoftware.com/pipermail/programming/2016-June/045277.html
The thread is worth reading as it shows works through the various issues that arose and explains the final version from Marshall Lochbaum mergerow=: ((* >:) #~ _1 |. -.@]) [: >/\.&.|. 2 =/\ ,&_1 If you are unaware, there is a 2048 addon available in JAL which uses the techniques above to implement the merges in all 4 directions. https://github.com/jsoftware/games_2048/blob/master/engine.ijs Cheers, On Thu, May 23, 2019 at 10:41 AM Luca Masini <lmas...@web.de> wrote: > Hi, > > I'm trying to come out with a few primitives for a 2048-like-game > operations. > > I did the following > > first =: {. > rest =. }. > f =: ((dyad def 'x,y')"(0 1)`(dyad def '(x + first y) , rest y'"(0 > 1))@.=) > > In words f should do the following > - if x = first y the reduce it to x+y > - if x not = first y then give back the sequence x,y > > > The intended use would be, for ex. > > f/ 4 4 4 > 4 8 > > f/ 4 4 4 4 > 8 8 > > In the first case it works. > > > In the second case the result is the following: > > f/ 4 4 4 4 > 8 0 > 4 8 > > My idea was > > f/ x x x x > > is equivalent to > 4 f 4 f 4 f 4 > > then, working right-to-left, 4 = first 4, so it simplify to > 4 f 4 f 8 > > now, 4 is not = first 8, so it should simplify to > 4 f 4 8 > > now, 4 is = first 4 8, so it should simplify to > 8 8 > > > What could be a way to implement the behavior that I described? > > MfG > > Luca. > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
