9 replies to this topic

[Sewbacca]

Look at this example:

{
  [1] = 'foo',
  [3] = 'foo2',
  [4] = 'foo3',
  [24] = 'foo4'
}

Which function allows to close gaps?
So into this:

{
  'foo', 'foo2', 'foo3', 'foo4'
}

[Creator]

Not visually, right? You mean the indexes?

newTable = {}
index = 1
for i,v in pairs(oldTable) do
  newTable[index] = v
  index = index + 1
end

[Yevano]

Creator, on 23 March 2016 - 09:31 PM, said:

Not visually, right? You mean the indexes?

newTable = {}
index = 1
for i,v in pairs(oldTable) do
  newTable[index] = v
  index = index + 1
end

This will change the array to be in random order, so if the order matters this won't work.

[Creator]

Yevano, on 23 March 2016 - 09:42 PM, said:

Creator, on 23 March 2016 - 09:31 PM, said:

Not visually, right? You mean the indexes?

newTable = {}
index = 1
for i,v in pairs(oldTable) do
  newTable[index] = v
  index = index + 1
end

This will change the array to be in random order, so if the order matters this won't work.

I believe pairs returns number indexes in the correct order.

[Lupus590]

ipairs instead of pairs

Edited by Lupus590, 23 March 2016 - 11:32 PM.

[KingofGamesYami]

ipairs wouldn't get to 14. It stops at the first nil (5).

local newTable = {}
for i = 1, table.maxn( oldTable )
  newTable[ #newTable + 1 ] = oldTable[ i ]
end

Logic: iterate from 1 to the largest index in oldTable (14). Each time, add an element to newTable. #newTable won't increase if the previous element in oldTable was nil, so it removes gaps.

[Lyqyd]

If the table starts out with no gaps, you can use table.remove to remove entries without creating gaps. It's much easier to keep your tables gap-free than to clean them up after introducing gaps. Of course, if your table starts out with gaps, you'd need to use one of the options above.

The best option may be to make a table containing the numeric keys, sort that table, then iterate that table and use the key/index pairs in it to move around values in the original table.

[Sewbacca]

Lyqyd, on 23 March 2016 - 10:30 PM, said:

If the table starts out with no gaps, you can use table.remove to remove entries without creating gaps. It's much easier to keep your tables gap-free than to clean them up after introducing gaps. Of course, if your table starts out with gaps, you'd need to use one of the options above.

The best option may be to make a table containing the numeric keys, sort that table, then iterate that table and use the key/index pairs in it to move around values in the original table.

I thought to use table.remove, but this would create issues.

Creator, on 23 March 2016 - 09:46 PM, said:

Yevano, on 23 March 2016 - 09:42 PM, said:

Creator, on 23 March 2016 - 09:31 PM, said:

Not visually, right? You mean the indexes?

newTable = {}
index = 1
for i,v in pairs(oldTable) do
  newTable[index] = v
  index = index + 1
end

This will change the array to be in random order, so if the order matters this won't work.

I believe pairs returns number indexes in the correct order.

I think this is the best solution, thanks.

[Yevano]

Creator, on 23 March 2016 - 09:46 PM, said:

I believe pairs returns number indexes in the correct order.

Not always, particularly if the input table is sparse. I'm guessing this happens because sparse indices will get shoved into the hash part of the table, though I don't know the exact behavior. I wouldn't rely on pairs for iterating in a particular order unless I was certain the input table only consists of an array part.

[Bomb Bloke]

Yevano, on 24 March 2016 - 09:53 PM, said:

I'm guessing this happens because sparse indices will get shoved into the hash part of the table, though I don't know the exact behavior.

That's exactly the way tables are constructed, yes: if the values are added in order and with no gaps, LuaJ sticks them into an array (occasionally making a new array and copying over all the old indexes if it runs out of room). If there are gaps between values, then they get hashmapped instead; otherwise, making a new table and sticking something into index 1000000 would result in LuaJ creating a stonking great array with nothing in it.