The length of the tail of the string is:
1 + length( all but the first character of the tail )
Keep doing this until there are no characters in the tail. Let us agree that the tail of a string that contains one character is the empty string.
The length of a string is:
This looks a lot like the "crossing the parking lot" procedure in chapter 70.
Does the "string length" definition have the two parts of recursion?