Regarding variable names within a loop

[andrew.207]

Kind of hard to explain, so I'll paste a small bit of code.

Code: Select all

 
for i=1, #bloops do       -- Outer loop for iteration
  local ev = bloops[i]
  for j = 1, 4 do
    ev.velocity = ev.velocity * ev.decel
    ev.y1 = ev.y1 + ev.velocity*dt
    ev.x2 = ev.x2 + ev.velocity*dt
    ev.x3 = ev.x3 - ev.velocity*dt
    ev.y4 = ev.y4 - ev.velocity*dt
  end
end

etc etc. The issue is having to type the number each time. Perhaps there is something weird string concatonation like ev.y+j that works? I can't find any through searching.

If not, easy no answer to stop me searching and change the "object"'s construction to accomodate.

Cheers!

[micha]

If the variables are just numbered, then it makes a lot of sense to use a table with numeric keys:

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ev.y[1] = ev.y[1] + ev.velocity*dt

As a rule of thumb: If you happen to write very similar code, multiple times, then this is a sign that you can simplify the code a lot.

Otherwise, if you have the name of a variable stored as a string, then you can access it with

Code: Select all

for i = 1,4 do
  name = 'y' .. i
  ev.[name] = stuff
end

The neat feature, here, is that you can use a string and sort of convert it to a variable name.

[andrew.207]

Exactly what I was looking for, cheers.

[raidho36]

That's really odd how he used array for entities but couldn't think of using it for coordinates.

[andrew.207]

It's for gibbing. Basically it drawn each limb of the object with its own X Y and sends them apart based on what caused it. I kinda figured one "object" with a larger set of coordinates was better than mutliple objects becuase memory.

[Plu]

You should generally not worry about memory and performance unless you're actually seeing it drag down, and even then only look for the worst offenders. You're most likely working on a machine with at least 1 gigabyte of memory, worrying over bytes of extra memory being used. You have close to a billion of them. You can afford to be a bit wasteful if it makes your code cleaner and more readable.