A "Snake" system.

ID:156834
 
Jul 17 2010, 7:41 am (Edited on Jul 17 2010, 7:47 am)
Hey guys, I am having some issues. I am trying to make a little game to play, based off of the old classic, "Snake". I have thought through many aspects of the game, and still do have some more.

My problem is this: How can I efficiently create and move a "link" correctly? I am using an associative list to manage how many links I have, and the links create right, and actually move decently too. But I still have some issues:

-A Runtime error associated with the code below:
runtime error: bad index
proc name: Add Body (/mob/proc/Add_Body)
source file: Procs.dm,28
usr: Albro1 (/mob/player)
src: Albro1 (/mob/player)
call stack:
Albro1 (/mob/player): Add Body()
Albro1 (/mob/player): Add Link()

-The associative list does not seem to be working correctly, meaning somewhere I have screwed up. Whenever I create one, it should go behind/beside(depending on the direction) the last created link, if there was one. Instead, it always goes behind me.

mob
    proc
        Add_Body()
            var/obj/O = new /obj/body(src.loc)
            if(src.trails)
                var/obj/N = src.trails["[src.trails.len] link"]
                O.dir=N.dir
                //movement stuff
                src.trails["[src.trails.len+1] link"]=O
            else
                var/mob/M = src
                O.dir=M.dir
                //movement stuff
                M.trails["1 link"]=O
Jul 17 2010, 2:55 pm
You don't need an associative list at all, here. Just a linked list, where each segment points to the previous one. Like so:

obj/body
  var/obj/body/previous
  Move()
    var/turf/oldloc = loc
    .=..()
    if(.)
      previous.Move(oldloc)

mob
  var/obj/body/previous
  proc/Add_Body()
    var/obj/body/B = new(loc)
    B.dir = dir
    if(src.previous)
      B.previous = src.previous
    src.previous = B
  Move()
    var/turf/oldloc = loc
    .=..()
    if(.)
      previous.Move(oldloc)
Jul 17 2010, 4:28 pm
In response to Garthor
Thanks. I have one problem though; how would I manage the links? If the mob turns, it doesn't necessarily mean a created link would turn just then. The body could become quite long, meaning the mob could be facing west while the last link could be facing south.
Jul 17 2010, 4:35 pm
In response to Albro1
Base the turns off of the last added object and not the head object.