Sum of the digits of an integer in lua

Question

I saw a question like this relating to Java and C, but I am using LUA. The answers might have applied to me, but I wasn't understanding them.

Could someone please tell me how I would get the sum of the individual digits of an Integer. For Example.

a = 275
aSum = 2+7+5

If you could explain how I would achieve this in LUA and why the code does what it does, that would be greatly appreciated.

Answer 1

Really a simple function. Using gmatch will get you where you need to go.

function sumdigits(str)
  local total = 0
  for digit in string.gmatch(str, "%d") do
  total = total + digit
  end
  return total
end

print(sumdigits(1234))

10

Basically, you're looping through the integers and pulling them out one by one to add them to the total. The "%d" means just one digit, so string.gmatch(str, "%d") says, "Match one digit each time". The "for" is the looping mechanism, so for every digit in the string, it will add to the total.