modify elements of arb.dimensionality matrices

*To*: mathgroup at smc.vnet.net*Subject*: [mg77218] modify elements of arb.dimensionality matrices*From*: "alexxx.magni at gmail.com" <alexxx.magni at gmail.com>*Date*: Tue, 5 Jun 2007 07:04:56 -0400 (EDT)

I was able to write an interface to deal with matrices having dimension defined at runtime (see http://groups.google.it/group/comp.soft-sys.math.mathematica/browse_frm/thread/f286f5bdafba4195/c85eaca115f18a46?lnk=st&q=+%22Alessandro+Magni%22&rnum=2&hl=it#c85eaca115f18a46). My last problem - more a performance problem - is modify access to those matrices: reading access at a given index location i (where i is the location {x,y,z,...}) is made with: >Extract[h, i] while to increment h[[]] at i I use: >h = ReplacePart[h, i -> Extract[h, i] + 1] but I really miss the possibility to write h[[x,y]]=h[[x,y]]+1, and I'm user there are serious performance issues with my solution. The nearest I came to a solution was with: >h[[##]] & @@ i = "x" but I immediately get: >Set::write: Tag Apply in (s[[##1]]&)@@{1,2,1} is Protected. >> Do you have any idea on this? thank you! Alessandro Magni

**Follow-Ups**:**Re: modify elements of arb.dimensionality matrices***From:*Carl Woll <carlw@wolfram.com>