Purely functional programming

Purely functional programming is a type of programming that uses only mathematical functions. In this type of programming, the same input will always get you the same output, and no part of the code will change the data stored in memory. This means that all of the data used by the program is stored in variables. This makes it easier to debug and troubleshoot the code if something isn't working correctly. It also makes it more secure because there isn't any risk of accidental data manipulation when the program is running.