Lua basics 01

Calculate factorial of a number.

-- Calculate factorial

function factorial(number)
    if number == 0 then
        return 1
    else
        return number * factorial(number - 1)
    end
end

-- Main function

function main()
    io.write("Enter the number to get the its factorial value: ")

    userInput = io.read("*number")

    if userInput == nil then
        print("User input is invalid.")

        os.exit()
    end

    number = factorial(userInput)

    io.write("factorial of ", userInput, ": ", number, "\n")
end

main()