Recursion (week 4- 5)

A recursive function is a function that its implementation references itself. I have been increasingly interested in recursive functions since I was introduced to the concept in the first lecture of this course. In plain English, a function can refer to its own header in the body so that it can execute itself over and over again and produce the result we want more efficiently.

During week 4, I learnt more about recursive functions. Specifically, I learnt about nested list and how to solve for the depth of a nested list. We started by defining the nesting-depth of L as 1 plus the maximum nesting depth of L's elements if L is a list, otherwise 0. Then I learnt that the code we write is almost exactly the same as the definition, that is, return (1 + max([nested_depth(x) for x in L] + [0]) if isinstance(L, list) else 0). we add [0] into L because we need to treat the depth as 0 in case we go through an empty list.

At first I was a little confused about what's going on because I don't quite understand why and how we can put a function header in its body to execute the code. However, by discussing with the person next to me during class and also by finishing up Assignment 1, I walked myself through both the definition and application of recursive functions. What's more, figuring out how to complement the codes in the Tour.py file in Assignment 1 gives me a more thorough understanding of recursive functions.

What I found most interesting about week 4's lectures was the turtle functions and how amazingly the "turtle" object can draw those pictures. As a very classic recursive object, turtle also refer to itself in the function body. the picture it drew impressed me a lot. The basic rule of how the turtle object works is like the growth of tree twigs, which is a lot like the picture below:

During the lab of week 5, I applied my knowledge gained previously and actually sat down and wrote some recursive functions together with my partner. We figured out that a recursive function will not stop running until the condition in the 'else' part is met. This concept makes my understanding of recursion even more clear.

Recursive functions are amazing and hopefully I'll learn more about them in the next few weeks.

SEE YOU NEXT WEEK! :)