Rob and Raul.. Thanks chaps for the comments...the first thing I need to do is write -something- that does something and then go from there. It's not really a maths problem... well, in a way everything is maths I guess but I am wanting to learn J and to write a game with it and that's pretty much it.
I'll post some progress somewhere someday... Thanks again Sean On Sun, 6 Dec 2020 at 21:41, 'Rob Hodgkinson' via Programming < [email protected]> wrote: > Sean, the data structures in J work brilliantly for mathematical array > type problems. > > When the data framework you are seeking is more “structured” (akin to > Tables and Columns, or Keys and Values), then a more suited structure might > require “jdb” for example (which makes use of boxing “tuples”). > This is a J compatible structured database for tables and columns. > > It really depends on the problem you are solving, for example for Advent > of Code or other coding challenges they are usually mathematical in nature > and the J arrays are perfect, as they can be rectangular arrays (matrices > etc) or nested arrays (boxed) so there is a lot of flexibility. > > With that in mind, I suggest learn the tools and then consider the > structure depending on the nature of the problem, but they are pretty well > all there for you to use. > > HTH Rob > > > On 7 Dec 2020, at 7:50 am, emacstheviking <[email protected]> wrote: > > > > Hauke, > > Thanks for your comments. I have been scribbling notes on howto go about > > it, my initial thoughts are that I need: > > > > genstar =: 3 : 0 > > generates an array of random numbers: initial x, initial y, dy, type > > > > updstar =: 3 : 0 > > in-place updates y by adding dy*timer interval > > if y is off screen then randomly reset this entry with y=0 > > > > Ha! This is going to be a lot of fun... > > > > > > > > > > On Sun, 6 Dec 2020 at 20:36, Hauke Rehr <[email protected]> wrote: > > > >> If the atoms of x, y and dy are all numbers (or tuples thereofª), > >> you can use a 3(or moreª)×(whatever common shape they have) array. > >> Index into them along the correct axes, and you’ll get > >> back (or modify) a triplet (or triplets) (again, or moreª). > >> > >> And updating ought to be done in place as much as possible. > >> You don’t do updating most of the time, but when you need to, > >> do it in place if at all possible. > >> You’re guaranteed to work in place if you immediately assign > >> back to the name of the structure you amend, for example. > >> Also, take a look at the special combinations. > >> Personally, I avoid boxing as much as possible. > >> > >> Then again, that’s just my thoughts and I’m far from > >> as experienced as the average person on this list, I guess. > >> > >> Am 06.12.20 um 21:13 schrieb emacstheviking: > >>> What's the conventional wisdom / best practice on defining data > >> structures > >>> for an application? > >>> > >>> Given there is no explicit keyword/operator support like C (typdef, > >>> struct) is it merely a case of convention and using boxed structures. > I > >>> have read several operators that can modify structures both as new > >> aliased > >>> copies and in-place modifications but I do not have the experience > with J > >>> to know what's efficient at run time in time / memory etc. > >>> > >>> My specific use case is that of a vertically scrolling star field... I > >>> intend to recreate and hopeful extend the tiny little game I wrote but > >>> never finished, screenshot here: > >>> http://seancharles.xyz/posts/2019-10-06-all-at-c.html > >>> > >>> In that I had a struct that had the x, y, dy and type values but it > seems > >>> to me that given that J is all about arrays, it might be more efficient > >>> using parallel arrays i.e. x array, y array, dy array etc. > >>> > >>> Also, given that the state is being updated in a tight event loop using > >> the > >>> time differential between frames to calculate the step motion (i.e. CPU > >>> speed independently), what are your thoughts on immutable updates > >> producing > >>> new arrays or updating in place ? > >>> > >>> Thanks, > >>> Sean. > >>> ---------------------------------------------------------------------- > >>> For information about J forums see http://www.jsoftware.com/forums.htm > >>> > >> > >> -- > >> ---------------------- > >> mail written using NEO > >> neo-layout.org > >> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > >> > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
