Lua table read and match efficient - function

Question

My problem is simple, i used to do this in order to check if any of my lines (see photo) bump into any other line (or trail of any other line). But the way i do this now is by doing a lot of if statements, which is not good. So here is the code i used:
function Bumper:draw()
for id,posx1 in pairs(tableposx1) do
posy1 = tableposy1[id]
posx2 = tableposx2[id]
posy2 = tableposy2[id]
posx3 = tableposx3[id]
posy3 = tableposy3[id]
posx4 = tableposx4[id]
posy4 = tableposy4[id]
if (posx1 ~= nil) and (posy1 ~= nil) and
((math.abs(xposplayer1 - posx1) < 5) and (math.abs(yposplayer1 - posy1) < 5))
and (id < (count - 5) and killp1 == "false") then
killp1 = "true"
tint(255, 0, 0, 162)
sprite("Dropbox:kill",xposplayer1,yposplayer1)
noTint()
end
if (posx2 ~= nil) and (posy2 ~= nil) and
((math.abs(xposplayer1 - posx2) < 5) and (math.abs(yposplayer1 - posy2) < 5))
and killp1 == "false" then
killp1 = "true"
tint(255, 0, 0, 162)
sprite("Dropbox:kill",xposplayer1,yposplayer1)
noTint()
end
if (posx3 ~= nil) and (posy3 ~= nil) and
((math.abs(xposplayer1 - posx3) < 5) and (math.abs(yposplayer1 - posy3) < 5))
and killp1 == "false" then
killp1 = "true"
tint(255, 0, 0, 162)
sprite("Dropbox:kill",xposplayer1,yposplayer1)
noTint()
end
if (posx4 ~= nil) and (posy4 ~= nil) and
((math.abs(xposplayer1 - posx4) < 5) and (math.abs(yposplayer1 - posy4) < 5))
and killp1 == "false" then
killp1 = "true"
tint(255, 0, 0, 162)
sprite("Dropbox:kill",xposplayer1,yposplayer1)
noTint()
end
if (posx1 ~= nil) and (posy1 ~= nil) and
((math.abs(xposplayer2 - posx1) < 5) and (math.abs(yposplayer2 - posy1) < 5))
and killp2 == "false" then
killp2 = "true"
tint(0, 29, 255, 162)
sprite("Dropbox:kill",xposplayer2,yposplayer2)
noTint()
end
if (posx2 ~= nil) and (posy2 ~= nil) and
((math.abs(xposplayer2 - posx2) < 5) and (math.abs(yposplayer2 - posy2) < 5))
and (id < (count - 5) and killp2 == "false")then
killp2 = "true"
tint(0, 29, 255, 162)
sprite("Dropbox:kill",xposplayer2,yposplayer2)
noTint()
end
if (posx3 ~= nil) and (posy3 ~= nil) and
((math.abs(xposplayer2 - posx3) < 5) and (math.abs(yposplayer2 - posy3) < 5))
and killp2 == "false" then
killp2 = "true"
tint(0, 29, 255, 162)
sprite("Dropbox:kill",xposplayer2,yposplayer2)
noTint()
end
if (posx4 ~= nil) and (posy4 ~= nil) and
((math.abs(xposplayer2 - posx4) < 5) and (math.abs(yposplayer2 - posy4) < 5))
and killp2 == "false" then
killp2 = "true"
tint(0, 29, 255, 162)
sprite("Dropbox:kill",xposplayer2,yposplayer2)
noTint()
end
if (posx1 ~= nil) and (posy1 ~= nil) and
((math.abs(xposplayer3 - posx1) < 5) and (math.abs(yposplayer3 - posy1) < 5))
and killp3 == "false" then
killp3 = "true"
tint(1, 255, 0, 162)
sprite("Dropbox:kill",xposplayer3,yposplayer3)
noTint()
end
if (posx2 ~= nil) and (posy2 ~= nil) and
((math.abs(xposplayer3 - posx2) < 5) and (math.abs(yposplayer3 - posy2) < 5))
and killp3 == "false" then
killp3 = "true"
tint(1, 255, 0, 162)
sprite("Dropbox:kill",xposplayer3,yposplayer3)
noTint()
end
if (posx3 ~= nil) and (posy3 ~= nil) and
((math.abs(xposplayer3 - posx3) < 5) and (math.abs(yposplayer3 - posy3) < 5))
and (id < (count - 5) and killp3 == "false") then
killp3 = "true"
tint(1, 255, 0, 162)
sprite("Dropbox:kill",xposplayer3,yposplayer3)
noTint()
end
if (posx4 ~= nil) and (posy4 ~= nil) and
((math.abs(xposplayer3 - posx4) < 5) and (math.abs(yposplayer3 - posy4) < 5))
and killp3 == "false" then
killp3 = "true"
tint(1, 255, 0, 162)
sprite("Dropbox:kill",xposplayer3,yposplayer3)
noTint()
end
if (posx1 ~= nil) and (posy1 ~= nil) and
((math.abs(xposplayer4 - posx1) < 5) and (math.abs(yposplayer4 - posy1) < 5))
and killp4 == "false" then
killp4 = "true"
tint(255, 0, 229, 162)
sprite("Dropbox:kill",xposplayer4,yposplayer4)
noTint()
end
if (posx2 ~= nil) and (posy2 ~= nil) and
((math.abs(xposplayer4 - posx2) < 5) and (math.abs(yposplayer4 - posy2) < 5))
and killp4 == "false" then
killp4 = "true"
tint(255, 0, 229, 162)
sprite("Dropbox:kill",xposplayer4,yposplayer4)
noTint()
end
if (posx3 ~= nil) and (posy3 ~= nil) and
((math.abs(xposplayer4 - posx3) < 5) and (math.abs(yposplayer4 - posy3) < 5))
and killp4 == "false" then
killp4 = "true"
tint(255, 0, 229, 162)
sprite("Dropbox:kill",xposplayer4,yposplayer4)
noTint()
end
if (posx4 ~= nil) and (posy4 ~= nil) and
((math.abs(xposplayer4 - posx4) < 5) and (math.abs(yposplayer4 - posy4) < 5))
and id < (count - 5) and killp4 == "false" then
killp4 = "true"
tint(255, 0, 229, 162)
sprite("Dropbox:kill",xposplayer4,yposplayer4)
noTint()
end
end
end
Here is my init:
-- Main
a = 1
gameover = 0
tx = 0
paused = 1
count = 0
stagecount = 0
player1count = 0
player2count = 0
player3count = 0
player4count = 0
-- Random hole times
thistime1 = 0
thistime2 = 0
thistime3 = 0
thistime4 = 0
-- Dead players
killp1 = "false"
killp2 = "false"
killp3 = "false"
killp4 = "false"
kills = 0
-- Touch control
touches = {}
-- Player direction
pi = math.pi
o5pi = 50 * pi
mo5pi = - (50 * pi)
minpi = - (100*pi)
-- Random start direction
r1t = math.random(0,o5pi)
r2t = math.random(mo5pi,0)
r3t = math.random(minpi,mo5pi)
r4t = math.random(o5pi,100*pi)
r1 = r1t / 100
r2 = r2t / 100
r3 = r3t / 100
r4 = r4t / 100
deltar1 = pi / 55
deltar2 = pi / 55
deltar3 = pi / 55
deltar4 = pi / 55
-- Player speed
speed1 = 2.5
speed2 = 2.5
speed3 = 2.5
speed4 = 2.5
-- Player random start position
xposplayer1 = math.random(123,300)
yposplayer1 = math.random(123,300)
xposplayer2 = math.random(123,300)
yposplayer2 = math.random(468,645)
xposplayer3 = math.random(724,901)
yposplayer3 = math.random(468,645)
xposplayer4 = math.random(724,901)
yposplayer4 = math.random(123,300)
-- Player coordinate tables
tableposx1 = {}
tableposy1 = {}
tableposx2 = {}
tableposy2 = {}
tableposx3 = {}
tableposy3 = {}
tableposx4 = {}
tableposy4 = {}
Now i tried doing the following, but failed because i dont now how to use variable variable names:
for id,posx[a] in pairs(tableposx[a]) do
posy[a] = tableposy[a][id]
if ((posx[a] ~= nil) and (posy[a] ~= nil))
and (math.abs(xposplayer[a] - posx[a]) < 5)
and (math.abs(yposplayer[a] - posy[a]) < 5)
and (id < (count - 5))
and (killp[a] == "false")
then
killp[a] = "true"
tintp[a]
sprite("Dropbox:kill",xposplayer[a],yposplayer[a])
noTint()
end
end
a = a + 1
if a = 4 then
a = 1
end
-- EDIT: i use is 4 times, for 4 players!
function Player:draw1()
fill(255, 0, 11, 255)
xposplayer1 = xposplayer1 + speed1 * math.cos(r1)
yposplayer1 = yposplayer1 + speed1 * math.sin(r1)
if player1count == 0 then
thistime1 = math.random(200,500)
end
player1count = player1count + 1
if player1count < thistime1 then
table.insert(tableposx1,count,xposplayer1)
table.insert(tableposy1,count,yposplayer1)
tint(255, 0, 0, 162)
ellipse(xposplayer1,yposplayer1,10,10)
noTint()
elseif player1count > thistime1 then
tint(255, 0, 0, 162)
ellipse(xposplayer1,yposplayer1,5,5)
noTint()
if player1count > thistime1 + 20 then
player1count = 0
end
end
end
-- EDIT
How should i do this correctly? Thanks in advance!
Image:

Answer 1

You probably don't really want variable variable names like you said, but you can do it...
All globals are accessible by table named _G, and you can access your global variables by doing this:
_G['killp1']
_G['killp2']
-- etc
You can then use string manipulation as usual.
local i = 1
_G['killp' .. tostring(i)] -- same as _G['killp1']
i = i + 1
_G['killp' .. tostring(i)] -- same as _G['killp2']
But this is going to get really messy, fast. What you probably want to do instead is start using objects. You object might look something like this:
Linething = { x = 0, y = 0, dead = false, speed = 2.5 }
function Linething:new(o)
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
function Linething:checkCollision(other)
if self.x - other.x < 5 and self.y - other.y < 5 then
self.dead = true
-- other stuff
end
end
function Linething:update(delta_t)
-- update the game logic
self.x = self.x + self.speed * cos(self.angle) * delta_t
self.y = self.y + self.speed * sin(self.angle) * delta_t
end
function Linething:draw()
-- do line drawing here
tint(255, 0, 0, 162)
ellipse(self.x, self.y, 10, 10)
noTint()
-- etc
end
-- in main:
linething1 = Linething:new()
linething2 = Linething:new()
linething1.checkCollision(linething2)
EDIT: Typically you want to seperate the game logic from the rendering. Most games have a loop that looks like this:
function main_loop()
while true do
delta_t = get_change_in_time()
update_all(delta_t)
draw_all()
end
end
-- where update_all is something like this:
function update_all(delta_t)
player1:update(delta_t)
player2:update(delta_t)
-- things in a table:
for _, x in pairs(table_of_x) do
x:update(delta_t)
end
end
-- and draw all is basically the same
function draw_all()
player1:draw()
player2:draw()
-- things in a table:
for _, x in pairs(table_of_x) do
x:draw()
end
end
It looks like your Player object has-a Linething object. So you might want to add a Linething object to the Player object and change Player:draw() to call players_linething:draw(). Then you can have 4 Player objects, which each have a Linething object. Does that make sense?

Answer 2

The problem is that you're using variables with subscripts (player1, player2, etc.) rather than arrays (player[1], player[2], etc.) which makes it impossible to iterate over them in a loop.
You should also be grouping related items together. Rather than player 1 being represented by a bunch of global variables:
player1count = 0
speed1 = 2.5
Those things should be organized into a table:
player1.count = 0
speed1.speed = 2.5
And, as mentioned before, any time you have a bunch of variables that vary by subscript, you should be using an array (or more generally, some kind of iterable list type, which in Lua happens to be a table/array):
players = {}
-- initialize players
for i=1,NUM_PLAYERS do
players[i] = {
count = 0,
speed = 2.5
}
end
If you apply this generally to your program, your huge if statement is going to naturally disappear, being replaced by a relatively small, nested for loop.

Answer 3

I have not read everything but in your last snippet:
You cannot do for id,posx[a], because the variables assigned by a for loop are local. To fix it replace instances of posx[a] by a local variable name such as posx_a.
There is a typo here: if a = 4 then (you mean ==).
This line means nothing: tintp[a].