Im new to lua and have a problem which i believe has an elegant solution, but i just cant make it work. I've read similar questions and answers here on stack overflow and elsewhere for hours as well as testing in online lua compiler but no real progress.
Q:
i start out with an empty table:
local vertices = {}
Now, with a for loop or similar i want to populate this table so the end result has this form:
local vertices = {
{x=-6.0, y=0.0},
{x=0.0, y=1},
}
Where the values in the entries {x=-6.0, y=0.0} are arbitrary, and the number of these {x=0.0, y=1} (coordinates) are also arbitrary.
These values are to be fetched from another table and som calculated in the for loop, but that is the next step. For now i just need help populate my empty table with x,y values in a loop.
Thanks to you all.
You can add elements to a Lua table through
the table constructor local t = { v1, v2, v3 }
assignment t[k1] = v1 t[k2] = v2
table.insert(t, 1) (for consecutive integer indices starting at 1)
rawset(t, 1, 1) if you want to avoid invoking metamethods
table.move to copy elements fro one to another table
...
For your case you can simply use assignment in a for loop.
local vertices = {}
for i = 1, 100 do
vertices[i] = NewVertex();
end
To add 100 vertices to the table.
Related
Reading the injected comments in the Code Snippet should give enough context.
--| Table |--
QuestData = {
["QuestName"]={
["Quest Descrip"]={8,1686192712},
["Quest Descrip"]={32,1686193248},
["Quest Descrip"]={0,2965579272},
},
}
--| Code Snippet |--
--| gets QuestName then does below |--
if QuestName then
-- (K = QuestName) and (V = the 3 entries below it in the table)
for k,v in pairs(QuestData) do
-- Checks to make sure the external function that obtained the QuestName matches what is in the table before cont
if strlower(k) == strlower(QuestName) then
local index = 0
-- Iterates over the first two pairs - Quest Descrip key and values
for kk,vv in pairs(v) do
index = index + 1
end
-- Iterates over the second two pairs of values
if index == 1 then
for kk,vv in pairs(v) do
-- Sends the 10 digit hash number to the function
Quest:Function(vv[2])
end
end
end
end
end
The issue I'm running into is that Lua will only pick up one of the numbers and ignore the rest. I need all the possible hash numbers regardless of duplicates. The QuestData table ("database") has well over 10,000 entries. I'm not going to go through all of them and remove the duplicates. Besides, the duplicates are there because the same quest can be picked up in more than one location in the game. It's not a duplicate quest but it has a different hash number.
Key is always unique. It is the point of the key, that the key is pointing to unique value and you can't have more keys with same name to point different values. It is by definition by Lua tables.
It is like if you would want to have two variables with same name and different content. It does not make sense ...
The table type implements associative arrays. [...]
Like global variables, table fields evaluate to nil if they are not initialized. Also like global variables, you can assign nil to a table field to delete it. That is not a coincidence: Lua stores global variables in ordinary tables.
Quote from Lua Tables
Hashing in Lua
Based on comments, I update the answer to give some idea about hashing.
You are using hashing usually in low-level languages like C. In Lua, the associative arrays are already hashed somehow in the background, so it will be overkill (especially using SHA or so).
Instead of linked lists commonly used in C, you should just construct more levels of tables to handle collisions (there is nothing "better" in Lua).
And if you want to have it fancy set up some metatables to make it somehow transparent. But from your question, it is really not clear how your data look like and what you really want.
Basically you don't need more than this:
QuestData = {
["QuestName"]={
["Quest Descrip"]={
{8,1686192712},
{32,1686193248},
{0,2965579272},
},
},
}
As Jakuje already mentioned table keys are unique.
But you can store both as a table member like:
QuestData = {
-- "QuestName" must be unique! Of course you can put it into a table member as well
["QuestName"]={
{hash = "Quest Descrip", values = {8,1686192712} },
{hash = "Quest Descrip", values = {32,1686193248} },
{hash = "Quest Descrip", values = {0,2965579272} }
}
}
I'm sure you can organize this in a better way. It looks like a rather confusing concept to me.
You've said you can't "rewrite the database", but the problem is the QuestData table doesn't hold what you think it holds.
Here's your table:
QuestData = {
["QuestName"]={
["Quest Descrip"]={8,1686192712},
["Quest Descrip"]={32,1686193248},
["Quest Descrip"]={0,2965579272},
},
}
But, this is actually like writing...
QuestData["Quest Descrip"] = {8,1686192712}
QuestData["Quest Descrip"] = {32,1686193248}
QuestData["Quest Descrip"] = {0,2965579272}
So the second (and then, third) values overwrite the first. The problem is not that you can't access the table, but that the table doesn't contain the values any more.
You need to find a different way of representing your data.
In the past I found myself using a table as index and value of
a table when the order was irrelevant.
Since every table returns a unique value they are save to use as
index and with that I already got all the information I want to
use later on in the program. Now I did not see any similar lua code
jet and didn't use it in a non test-program. So I'm worrying that I
might get some unforeseen/unexpected problems when using this method.
example:
a = {1,2,3,4,5} --some testing values
b = {2,nil,4,nil,1}
c = {3,nil,nil,nil,2}
d = {4,nil,1,nil,3}
e = {5,1,2,3,4}
tab = {a,b,c,d,e}
t = {}
for i, v in pairs(tab) do
t[v] = 0
end
for iv in pairs(t) do --is almost every time outputting it in a different order
print(iv[1],iv[2],iv[3],iv[4],iv[5]) --could be a list of data where you have to go through all of it anyway
end
io.read()
Now I can store some additional information in t[v] but if I don't have
any is there maybe some lua-type that is smaller?
Edit:
Does this go well with the use of weak-tables?
Note:
Standard 2d table: table[key1] = table
table[key1][key2] <-- contains stuff
this version: table[table] = anything but nil <-- not accessible over table[key1][key2]
key1[key2] <-- contains stuff
It's fine to use a table as a key in another table.
However, note that different tables will be different keys, even of the tables have the same contents.
I want to delete all entries from a table, wich equals a given value.
Now, I got a pretty little problem one might to know, how to handle.
This is the Code:
function(list_to_search_in, compared_value, invert)
for k,v in pairs(list_to_search_in) do
if invert and v ~= compared_value then
table.remove(list_to_search_in, v)
if not invert and v == compared_value then
table.remove(list_to_search_in, v)
end
end
end
The Problem:
Let's say the table is { 1, 2, 3, 2 }. So when I'm iterating through that loop and come to the first match, it's removed from the table. This means the value and the key is deleted.
Now the key of the deleten value is assigned to the next value in line. But due the skript will check the value of the next key, this value (whichs kay has been just altered) will never be checked.
I thought, a simple
k = k - 1
after a remove would do the job, but it doesn't.
v = nil
would do great I think, but only if garbage-collector does not do his job in this very moment the pairs iterates to the next value.
Anyone has an idea? I would prefer an text-based hint to a finished syntax which solves the problem.
Don't use table.remove for this. It squeezes the "hole" out of array-like tables. That's not allowed during an iteration using pairs/next. Just set the value to nil.
If you need to squeeze holes out of the table then you can either create a new table and populate it with only the values you want to keep or do the removals during the first pass and then squeeze out holes in a second pass.
Also the order of item traversal when using pairs is not guaranteed in any way.
I have searched around quite a bit and couldn't quite find a solution for this. Any help you can offer would be appreciated.
-- The array compiled of enemies only allowed in the current
-- level phase
local EnemyList = {}
-- Counter to determine the next spot in the EnemyList
-- array to insert into
local counter = 1
for i=1,#Enemies do
if Enemies[i].phase == 0 or Enemies[i].phase == which_phase then
EnemyList[counter].src = Enemies[i].src
EnemyList[counter].exp = Enemies[i].exp
counter = counter + 1
end
end
I am getting an error about attempting to index a nil value, in reference to the EnemyList table/array. What I am trying to accomplish is I am trying to compile a new array of only enemies that are allowed. I guess I am unsure how to insert a new row into the EnemyList table. I tried using table.insert, but the value parameter is required, and I am not sure how to do that with the fact that I am storing multiple values into the EnemyList array.
Any help or insight on the proper way to insert a new row into an empty table/array would be much appreciated. Thanks!
EDIT:
I got a working solution, but I figured I should update the code here if anyone in the future finds it.
-- The array compiled of enemies only allowed in the current
-- level phase
local EnemyList = {}
for i=1,#Enemies do
if Enemies[i].phase == 0 or Enemies[i].phase == which_phase then
table.insert( EnemyList, { src = Enemies[i].src, exp = Enemies[i].exp } )
end
end
You can store tables within tables in Lua. Tables are indexed in one of two ways: First, by index number. This is what table.insert uses; it will add an entry at the next index number.
The second way is by key; e.g.
> t = {}
> t.test = {}
> =t.test
table: 0077D320
You can insert tables into tables; this is how you create a 2D table. Because of the way you've defined your tables, type(EnemyList[counter]) = table.
You can insert new entries into tables by running table.insert(table, value). This will assign value to the next available numeric entry. type(value) can also be a table; this is how you create "multidimensional arrays" in Lua.
As an aside, instead of using for i=1,#Enemies I would suggest using for i,v in ipairs(Enemies). The second one will iterate over all numerical entries in the Enemies table.
from the below
Control Panel\Programs\Programs and Features
Need the List view in the Lua table
Suppose the Name of the Program installed , its version and size etc.
Issue is Lua seems to doesn't takes two argument like two dimension array
Using Lua table you can store List of string
But how to store a two dimension array ?
table = {}
for i = 1, 10 do
table[i] = {}
for j = 1, 10
table[i][j] = i+j
end
end
A multidimensional array in Lua is simply multiple tables in another :), one for each row/col.
Oh and another option is faking a multidimensional array through some simple arithmatic, something like: table[x+rowlen*y]