LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
Can someone give me a detailed tutorial on how arguments in functions work, and also how 'return' works. I've read just about everything on the wiki but the descriptions are short and usually only show a small example.
Thanks. |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
When you want to call a function, sometimes it needs information. Like if you created a function that damages all players, it needs to know how much damage to do. Or if you write a function that gives a player a weapon, you need to tell it which player to give it to.
And in that same situation of taking damage, maybe you wanted to know how much total damage was given so you add up all the damage given and return the sum.
local function damageAllPlayers(amount)
local total = 0;
local players = game.Players:GetPlayers();
for idx = 1, #players do
local humanoid = players[idx].Character.Humanoid
local damage = math.min(humanoid.Health, amount);
total = total + damage;
humanoid:TakeDamage(damage);
end
return total;
end
print("Damage given to all players: " .. damageAllPlayers(50)); |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
I don't understand what 'amount' is, how exactly is that defined in the code?
How is the argument defined as a value or string or even an object?
And what does return do? Or more why is it needed? |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
amount is just a local variable that is set by the caller, when I did: 'damageAllPlayers(50)', I passed 50 as an argument, so the amount parameter (really just a local variable in Lua) was set to 50.
Return will stop execution of the function and return control back to the caller, meaning if you place a return like this:
function abc()
if true then return end
print("hi")
end
hi will never be printed. Optionally you can return values from a function meaning the caller will get them back, so if I did this:
function abc() return 123 end
local num = abc()
print(num)
123 would be printed since the function returned 123 (you can return multiple values too) |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
Ok I'm starting to understand it, I gotta get to sleep so I l'll look at this more tomorrow, thanks a lot. |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
Another way to think about it is in an algebraic sense.
You've probably taken a couple of math classes in your life and used functions:
f(x) = 3x
That function (f) would take an input (x) and return an output (3x).
If you think of the inputs as parameters and the outputs as return values, it might make more sense.
function f(x)
return 3*x
end |
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local function example(x, y)
print(x + y)
end
example(32, 96) --[[> 128, this is the line we call the function on.]]
Arguments are passed when you call the function.
You can have as little as 0, and as many as...Theres a limit but I forget what it is, its larger than anything you would ever need.
You also don't have to pass them when you call the function, if will be automatically passed as nil if you don't
(In my example function, example(32) or example() would both call the function normally but the print line would error that x or y is a nil value)
You can also pass more than the needed ammount of arguments (example(32, 96, 128)) but the extra arguments just don't do anything so theres not a reason to so it.
You can also pass a tuple of arguments, most commonly used to pass an unknown number of arguments without needing to directly pass a table.
Its used like this.
(The tuple is basically an unpacked table so doing {...} will 'repack' it)
local function example(...)
for _, value in next, ({...}) do
print(value)
end
end
example("a") --[[> a]]
example("a", "b", "c") --[[> a
b
c]]
You see tuple used in functions like math.max like this
print(math.max(1, 2, 128, 4, 8)) --[[> 128]]
--[[math.max is basixally this]]
local function max(...)
local array = {...}
table.sort(array)
return (array[1]);
end
You can also use regular arguments with tuple arguments as long as you do the tuple last.
local function example(x, y, ...)
for _, z in next, ({...}) do
print((x + y) + z)
end
end
example(1, 2, 4, 8, 16) --[[> 7
11
19]] |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
I'm confused on exactly why you would use a function/tuple, why make a function to lets say create a IntValue and parent it to the workspace as apposed to just typing.
Instance.new("IntValue",workspace)
local function example(...)
for _, value in next, ({...}) do
Instance.new(...)
end
end
example("IntValue",workspace,"StringValue",workspace)
^ How would I get this to work? I'm trying to create the intvalue and string value but it only creates the intvalue.
Also how would I get this to work?
local function max(...)
local array = {...}
table.sort(array)
return (array[1]);
end
I tried
print(max(53,75,26,103)) -- The output will put out the 2nd number '75' instead of 103?
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
To get your first one to work, they're separated in pairs so something like:
local function example(...)
local arguments = {...};
for key = 1, #arguments, 2 do
Instance.new(arguments[key], arguments[key + 1]);
end
end
And for max (even though a math.max already exists lol):
local function max(...)
local array = {...}
table.sort(array)
return (array[#array]);
end |
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In your example there isn't a reason to use a function instead of just using Instance.new()
But sometimes using a function can make your script more efficent or just easier to write. |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
Technically, using a function will almost never make your script more efficient. Just more manageable and readable, which might lead to writing more efficient code. |
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71428Join Date: 2015-08-06
Post Count: 339 |
"Technically, using a function will almost never make your script more efficient"
I agree by I rather not have my eyes pierced every time I read some random script. I suggest everyone to always follow this format, not for their sake but for the rest of everyone else.
Which one would you rather?
function spawnwhatever()
return Instance.new("wa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39acwa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39ac")
end
--Spawn three i9d-qi9-q-wdk9-qw things
local x = spawnwhatever()
local y = spawnwhatever()
local z = spawnwhatever()
or
local x = Instance.new("wa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39acwa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39ac")
local y = Instance.new("wa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39acwa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39ac")
local z = Instance.new("wa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39acwa90eruiq9-rui9-qaci9-aui9-djaipwdmkpawdjipaj39urf9-ajfpiajf9pija3pf9ja3pifja3p9fja39pfjaipcjipajcp9a3j9cja39pcj39pacjpacpia3jcip3ajc90a3jcpa3cjipa3cj99a3pc39ac")
Yes it's a massive exaggeration but you get the point. |
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WrathsongJoin Date: 2012-07-05
Post Count: 22393 |
https://www.youtube.com/watch?v=4uYbUzk08FA |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
71428 must be one of those people who see a single part of a post and jump to conclusions without reading the rest. |
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71428Join Date: 2015-08-06
Post Count: 339 |
I was expanding my agreement on that point alone. I wasn't arguing with you. |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
I'm not sure if you already explained this but, what exactly does the return do?
You gave me this script.
local function max(...)
local array = {...}
table.sort(array)
return (array[1]);
end
What does return do? Why is it needed? |
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WrathsongJoin Date: 2012-07-05
Post Count: 22393 |
If you want a function to RETURN something, that just means you want it to give you something back. It could be a bool (true or false value) an integer value, a CFrame or position
https://www.youtube.com/watch?v=khh-GmEhO5Q |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
function x()
print(5+5)
end
x()
That above doesn't have a return and it gives me the sum of 10, I don't really get why you need to return something from a function, what exactly does the return get you I don't see why you need the return or what it does. |
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WrathsongJoin Date: 2012-07-05
Post Count: 22393 |
When you need to perhaps calculate an *unknown* value from a function |
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cntkillmeJoin Date: 2008-04-07
Post Count: 49450 |
local players =game.Players:GetPlayers()
The GetPlayers function has to return something so you can actually get a list of all the players. |
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WrathsongJoin Date: 2012-07-05
Post Count: 22393 |
^
kinda hard to explain to beginners.
Methods/custom functions like GetPlayers() always return something. For example, GetPlayers() returns a table of all players in a game. FindFirstChild() returns whatever you're searching for with it if it'd found, else it returns nil. |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
function d()
local players = game.Players:GetChildren()
for i = 1,#players do
print(players[i])
end
end
d()
No return and it runs, the output prints out the players. Sorry if I'm being a pest I just really want to learn this right and really understand it. |
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WrathsongJoin Date: 2012-07-05
Post Count: 22393 |
nah you're fine. not all of your custom functions need to have a return at the end. but all ROBLOX methods will return something, like GetChildren as you used above. you know because you iterated through it. it returns a table. what your function does is print the table it got. |
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LiLEViLJoin Date: 2008-05-04
Post Count: 161 |
Ok, I just don't get why we need to actually type return in the code? Like here
local function max(...)
local array = {...}
table.sort(array)
return (array[1]);
end
Like is there a case where the code wont run unless you return something manually?
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