Question

I have a table of strings. I’d like an easy way to remove all of the duplicates of the table.

So if the table is {a, b, c, c, d, e, e} , after this operation it would be {a, b, c, d, e}

Alternatively, and probably preferably, is there a way to add an element to a table, but only if it is not already contained within the table.

<\noobquestion>

Answer 1

What I normally do for this is index the table on the string so for example

tbl[mystring1] = 1
tbl[mystring2] = 1

etc.

When you add a string you simply use the lines above and duplicates will be taken care of. You can then use a for … pairs do loop to read the data.

If you want to count the number of occurrences

use something like

if tbl[mystring1] == nil then
  tbl[mystring1] = 1
else
  tbl[mystring1] = tbl[mystring1] + 1
end

As the end of the addition cycle if you need to turn the table around you can simply use something like

newtbl = {}
for s,c in pairs(tbl) do
  table.insert(newtbl,s)
end