Problem: Determine the Number of Digits in an Integer

• Want a procedure num-digits that behaves like:

  Expression	Value
  (num-digits 9475)	4
  (num-digits 1234567890)	10
  (num-digits 0)	1

• Q: What similar, smaller problem is such that, if you had a solution to it, would make the overall problem easy?

  A: The problem of determining the number of digits in an integer that is one digit smaller.

  Example:

  Number of digits in 9475	=	Number of digits in 947	+	1
  	=	3	+	1
  	=	4

• Q: How can we obtain 947 from 9475?