Lua - Format integer

Question

i\'d like to format a number to look as follows \"1,234\" or \"1,234,432\" or \"123,456,789\", you get the idea. I tried doing this as follows;

function ref         


        

Answer 1

You can do without loops:

function numWithCommas(n)
  return tostring(math.floor(n)):reverse():gsub("(%d%d%d)","%1,")
                                :gsub(",(%-?)$","%1"):reverse()
end

assert(numWithCommas(100000) == "100,000")
assert(numWithCommas(100) == "100")
assert(numWithCommas(-100000) == "-100,000")
assert(numWithCommas(10000000) == "10,000,000")
assert(numWithCommas(10000000.00) == "10,000,000")

The second gsub is needed to avoid -,100 being generated.