Week 7

Week 7: Recursion

There is an assigned topic for this week's slog: recursion! To begin, a simple definition of recursion would be a situation where, in a function body, the function itself is called. A function body, however, cannot contain only recursive calls as this would lead to an endless recursion loop. This problem is solved by having a base case, which is a piece of non recursive code that the function implements under certain conditions.

Over the past four weeks since recursion was introduced, the most common case I have seen in which recursion is used is nesting. For example, the first recursive function written in class was to find the sum of a nested list. Since then, we have written more functions for nested lists, and have been introduced to various other recursive structures. That includes trees, linked lists, and search lists from the lab, which are recursive because they may contain other instances of themselves nested within them. Another case where recursion is used, and this is where I was first introduced to the concept of recursion, is in a mathematical function, where the result is dependent on the previous result(s). For example, the week five reading mentioned the Fibonacci sequence, and the function M(n) used to find the minimum number of moves required for moving n number of cheeses from A1 use recursion. Last, an additional use of recursion could be drawing pretty fractal pictures.

When this topic was first mentioned, I thought it was strange that the function could call itself again without finishing its original call. But now I understand that in order to finish the original call, the function needs to call itself in order to solve the “sub-problem” and use that result in finishing the first call. The first time I wrote recursive function, I was overly concerned with my base case because I was worried about the endless loop, but as I got more practice, I was better able to write an effective solution with considerable confidence and with a better understanding of how the function is implemented. Also, I now see why this would be useful. For example, in the case of nesting, it is much more simple and efficient to write recursive code than to write non recursive code. That is because for a large degree of nesting, one would need to write a large number of repetitive code segments in order to deal with each degree of nesting while writing a recursive call only would take up one line. Reading that one line is also easier to understand than numerous lines of repetition. Overall, I find recursion to be an interesting topic.