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Table Preferences
Posted: Sun Jun 13, 2010 11:31 am
by Lap
I've tend to use something like:
Code: Select all
tbl = {}
tbl.Bread = true
tbl.Milk = true
if tbl.Bread then
print("We got some bread")
end
However, almost everyone else I see tends to do
Code: Select all
tbl = {}
table.insert(tbl,'bread')
table.insert(tbl,'milk')
if table.HasValue(tbl,'bread') then
print("We got some bread")
end
Is there a reason I shouldn't be using my current method for indexes of unique values?
Re: Table Preferences
Posted: Sun Jun 13, 2010 2:32 pm
by kikito
By using table.insert the table is indexed by continuous integers (1,2,3, etc).
This makes possible to iterate over the table with ipairs instead of pairs, so iterating over the table is more efficient.
It is also possible to automatically calculate the table length with #tbl.
Integers also take a little bit less memory - but not much more.
So table.insert is better with tables that are going to be iterated over a lot, and where the keys don't "matter" (so you can use numbers). Typically these are "lists of elements": lists of enemies, items, tiles on a map... that sort of thing. On these lists you normally don't know exactly how many elements you will have.
On the other hand, for us humans it is much easier to understand if you say tbl.body instead of tbl[2], for example.
On the efficiency department, table.insert is a function; It's slower than doing tbl.key = value.
So tbl.key = value is better when the table isn't going to be parsed over with a loop, or the keys have a "meaning" for the programmer. These are typically "object-like"; the element returned by tbl.key is "a property" of tbl, not an element on a list. On this kind of tables you know exactly how many keys you will have, and each has one name.
In your example I'd use table.key.
Re: Table Preferences
Posted: Sun Jun 13, 2010 3:05 pm
by bartbes
Oh, and as I pointed out in IRC the table.insert way supports duplicates.
Re: Table Preferences
Posted: Sun Jun 13, 2010 3:13 pm
by Robin
Also, table.HasValue() doesn't exist -- you'll have to write it yourself.
Re: Table Preferences
Posted: Sun Jun 13, 2010 4:56 pm
by Lap
Robin wrote:Also, table.HasValue() doesn't exist -- you'll have to write it yourself.
Speaking of which...
viewtopic.php?f=3&t=1637