Problem 44064. adding huge numbers

Write function called huge_add that adds together two positive integers of any length specified as char vectors using decimal notation. The single output argument is the result and it is a char vector as well. The inputs and output must contain digits only; no commas, spaces or any other characters are allowed. If any of these assumptions are violated by the input, the function returns the number -1. Hint: you cannot use any of the built-in numerical data types of MATLAB to do the calculation since the function needs to work for numbers that are larger than what can be represented as a number in MATLAB.