Why is my Lua if-else not working properly?

Question

print("Type a number:")
firstNum = io.read()
print("Type another number:")
secondNum = io.read()
print("First: " .. firstNum .. "\nSecond: " .. secondNum)
if firstNum > secondNum then
  print("first is bigger than second")
elseif firstNum < secondNum then
  print("first is less than second")
else
  print("first is equal to second")
end

Input:
firstNum = 5
secondNum = 15
Output:
first is bigger than second
Why is that happening?

Answer 1

firstNum and secondNum are strings, and "5" lexicographically comes after "15" because it starts by comparing the first characters only : '5' > '1' .

You need to convert them to numbers before comparing.

print("Type a number:")
firstNum = tonumber(io.read())
print("Type another number:")
secondNum = tonumber(io.read())
if firstNum > secondNum then
  print("first is bigger than second")
elseif firstNum < secondNum then
  print("first is less than second")
else
  print("first is equal to second")
end

This prints the expected first is less than second .