handling Throw exception in Lua

In Lua, you can throw an exception or raise an error using the error() function. This function accepts an error message string as the first argument and optionally a level number as the second argument, which indicates the level in the call stack where the error occurred. Here are some examples:

Example 1: Raise an error with a custom error message and the default error level.

-- This function takes a number as input and returns its reciprocal.
function reciprocal(num)
  if num == 0 then
    -- If the input is zero, raise an error with a custom message.
    error("Error: Cannot calculate reciprocal of zero.")
  else
    return 1 / num
  end
end
-- Call the function with valid input.

print(reciprocal(2)) -- Output: 0.5
-- Call the function with invalid input.

reciprocal(0) -- Output: Error: Cannot calculate reciprocal of zero.

Example 2: Raise an error with a custom error message and a specific error level.

-- This function takes a string as input and returns its length.
function string_length(str)
  if type(str) ~= "string" then
    -- If the input is not a string, raise an error with a custom message.
    error("Error: Input parameter must be a string.", 2)
  else
    return #str
  end
end
-- Call the function with valid input.

print(string_length("Hello")) -- Output: 5
-- Call the function with invalid input.

string_length(123) -- Output: Error: Input parameter must be a string.

In both examples, when an error is raised, the execution of the program stops immediately and the error message is printed to the console.