Require help with tables

[Jaykin]

I have searched around the forums and other places online, but I can't find any information on tables that I can get my head around. Does anyone know of any good information which explains tables well for use in Love? Thanks a lot!

[coffee]

I have searched around the forums and other places online, but I can't find any information on tables that I can get my head around. Does anyone know of any good information which explains tables well for use in Love? Thanks a lot!

Tables in LOVE are the same than Lua (the language code behind LOVE) tables:
http://lua-users.org/wiki/TablesTutorial
http://lua.gts-stolberg.de/en/Tables.php
http://www.troubleshooters.com/codecorn ... tables.htm

There's a lot more, but those should be good for now.

[Jaykin]

I do vaguely understand the concept generally, it's just applying it to Love I find difficult.

[Jasoco]

It's not that difficult really. Tables are easy. They can contain anything at all. Including, but not limited to, numbers, strings, functions, booleans, image data, font data, sound data, other data, other tables. And those other tables can contain any of that stuff too, including other tables.

They're written as such:

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table = {
  thing1 = whatever,
  thing2 = whatever,
  ...
}

OR

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table = {}
table[1] = whatever
table.thing1 = whatever
table["a string"] = whatever
table[a_variable] = whatever
...

Very versatile. Don't know how we'd make it any clearer.

[Jaykin]

Thanks, that does make sense. However the for i,v ipairs or pairs is what gets me...

[Kadoba]

A table is just a container for data. For every entry into the table there must be a key (also called an index) and a value.

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-- Create an empty table
local person = {}

-- Create new data in the table
-- "name" is the key and "Bill" is the value
person["name"] = "Bill"

--"age" is the key and "Bill" is the value
person["age"] = "23"

-- If the key is a string you can do this as a shortcut:
person.gender = "male"

for key, value in pairs(person) do
    print(key, value)
end
-- Prints:
-- name    Bill
-- age    23
-- gender    male

If you make a list of contents when you first create a table then those contents have numbers as keys.

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local t = {"one", "two", "three"}

for key, value in pairs(t) do
    print(key, value)
end

-- Prints:
-- 1     one
-- 2     two
-- 3     three

pairs and ipairs are functions that return what's called "iterators". When you use iterators in a for-loop they go over every key and value pair inside of a table (this is why the functions are called "pairs"). They're useful if you want to apply something to everything inside of a table

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-- Create a table of three numbers
local numbers = {1, 5, 10}

-- Multiple all numbers by 5 and store it back
for key, value in pairs(numbers) do
    numbers[key] = value * 5
end

-- Multiple all numbers by 3 and store it back
for key, value in pairs(numbers) do
    numbers[key] = value * 3
end

-- Print all pairs
for key, value in pairs(numbers) do
    print(key, value)
end

-- Prints:
-- 15
-- 75
-- 150

[Jaykin]

Thanks a lot! That was extremely helpful

Does anyone have any examples of how it is applied in a simple game?

[Jasoco]

A thing to remember is that ipairs() will only iterate over a table whose children are numbered in order from 1 on. Any gaps and it will stop. So if you have a table with things at 1, 2, 3, 4, 5 it'll run 1 to 5 with no problem. But leave one out, 1, 2, 4, 5 and it will stop at 2 instead. pairs will instead run over all items in the table, even ones with no specified index and any index you choose. But it might be a TINY BIT slower, but usually not noticeable. Also, pairs will not start at 0 and will always start at 1. So if you're used to languages where arrays begin at 0, get used to using 1 instead.

for i, t in ipairs(table) do would be the equivalent to for i = 1, #table do where the # part returns the "length" of a tables numerically indexed children. (Also remembering how the numbers have to be in order.)

When removing a table child using table.remove, remember that if you are currently in a ipairs() loop, you will throw everything off so, as was mentioned elsewhere a few days ago, make sure to go backwards through the table. (for i = #table, 1, -1 do where -1 means to step backwards and it starts at the end of the table and goes towards the beginning.) table.remove will remove a child, and then reconfigure everything to keep them in order. For instance if you have 1, 2, 3, 4, 5 and you table.remove 2, it'll then move 3 to 2, 4 to 3 and 5 to 4. Also remember this will slow things down with larger tables since it is literally for looping through every table element to move them.

I hope that didn't confuse the crap out of you. That's all slightly more advanced. Start slow and play around a bit to get used to it. You'll see how awesome tables are.

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table = {
  item = {
    item = {
      item = {
        item = {
          item = {
            value = "Hahaha!!!"
          }
        }
      }
    }
  }
}
print(table.item.item.item.item.item.value)

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> Hahaha!!!

Edit: I edited it so hopefully it's correct now. If not, it's Nixola's fault.

[Qcode]

Lets say you have multiple enemies, they all are basically the same but you need to keep all of them moving. You could use it to do that.

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enemy = {} 
enemy[1] = {x = 0, y = 0}
enemy[2] = {x = 30, y = 30}
for key, value in pairs(enemy) do
   enemy[key].x = enemy[key].x + 30
   enemy[key].y = enemy[key].y + 30
end

Theres a silly little example of how they'd both move in a game. Assuming they're all drawn at their own respective x and y's then the 2 enemies will move in the same way, at their different places.

[Nixola]

Jasoco, you confused pairs and iparis, it's the opposite