June 29, 2018

Recently, at a beginning programmer’s forum, I saw a user asking about the function length that finds the length of a list. He gave a simple version of length, then used it find the lengths of two lists and determine which was shorter. He correctly realized that calculating the full lengths of both lists is inefficient if one list is much longer than the other, and he asked if there was a way to run through the lists simultaneously, stopping as soon as it is known which list is shorter.

Your task is to write length and a function to determine which of two lists is shorter; your solution must use recursion. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.


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