In programming languages, characters have a corresponding numerical value. In the older days, this was known as ASCII value, now there's an extended set called Unicode values. The Unicode values for 'A' to 'Z' are 65 to 90 in sequence. The Unicode values for 'a' to 'z' are 97 to 112 in sequence. The Unicode values for '0' to '9' are 48 to 57 in sequence. Define a function that when passed an integer (assuming it's between 48 and 57), returns the digit (as a character) corresponding to it.