Error "attemped to compare number to string" lua, starter and probably easy to answer

Question

What is wrong with my code? this is a really easy fix I bet but I am pretty new to Lua so I cannot figure it out. The code is a random number generator that you are supposed to guess the number (its obviously not done) but it says "Lua: main.lua:8: attempt to compare string with number" here is the code

local number2 = math.random(1,100)
local hi=2
repeat
    print("pick a number, 1-100")
    local number = io.read ()
    if number == number2 then print("you got it!! congrats")
      end
    if number <= number2 then print("too high!")
      end
    if number >= number2 then print ("too low!")
      end
until (hi)==2

Answer 1

The problem is that io.read() returns a string - the next line of stdin, typically the user's input - rather than a number. Testing a string against a number - or any two values of different types - for equality in Lua always yields false. Thus number == number2 will always be false and you'll fall through to number <= number2. This raises the exception you're seeing; <= is well defined for two numbers or two strings, but not for a number and a string (should it compare lexicographically or numerically?), so Lua does the sensible thing and throw an error.

The fix is simple: You have to convert the user's input using tonumber or read a number. You can do the latter using io.read("*n"). It is possible that io.read("*n") returns with nil if the input was invalid, so we have to handle that.

Here's the fixed code:

local secret_number = math.random(1, 100)
repeat
    print("pick a number, 1-100")
    local guess_number = io.read("*n")
    if not guess_number then print("invalid input!")
    elseif guess_number < secret_number then print("too low!")
    elseif guess_number > secret_number then print("too high!") end
until guess_number == secret_number
print("you got it!! congrats")

Note that since you were not setting hi, the loop would have continued forever, rather than only exiting after the number has been guessed. Also, your "too low" and "too high" messages were swapped.