If I wanted to represent a matrix of objects.... say a world populated by virtual creatures... I might prefer to predefine the size of the world and identify creature locations using numeric coordinates. I might then want to use an array of arrays to represent the world ^^. I might even abstract away the position of an object using a "location" type composed of a pair of numeric coordinates and a reference to the world, then have "north" and "east" etc. functions to get locations in those directions. Then I might get the reference or set the reference of a location object and thus query and/or change the state of the creatures in that world.... ^^
In Arc-F for example I might use:
(using <vector>v2) ; vector and vector-of
(def make-world (xwidth yheight)
(apply vector
(w/collect:for i 0 (- xwidth)
(collect:vector-of yheight nil))))
; create a location type
(def location (world x y)
(annotate 'location
(list world x y)))
(defcall location (r)
(let (world x y) r
(world.x y)))
(defm sref ((t loc location) val)
(let (world x y) (rep loc)
(sref world.x val y)))
; 0---> INF
; |
; |
; v
; INF
(def south (loc (o step 1))
(err "'north and 'south expect a location"))
(defm south ((t loc location) (o step 1))
(let (world x y) (rep loc)
(location world x (+ y step))))
(def north (loc (o step 1))
(south loc (- step)))
(def east (loc (o step 1))
(err "'east and 'west expect a location"))
(defm east ((t loc location) (o step 1))
(let (world x y) (rep loc)
(location world (+ x step) y)))
(def west (loc (o step 1))
(east loc (- step)))
I should put some more work into it. The good news is that I just found a nice and simple editor that plays well with arc-f on windows (LispIDE - http://www.daansystems.com/lispide/)
btw. arc-f arc.bat doesn't play nice yet with "Program Files" type of directories. Works fine in C:\arc-f.
Got this error:
> default-load-handler: cannot open input file: "C:\Program" (The system cannot find the file specified.; errno=2)
