https://medium.com/software-design/pure-functions-in-c-fc102fd9c5e0 >C++ is not a functional programming language. Functions causing side-effects is the norm. If a compiler does not see the body of a function, it assumes that the function causes side effects. This can result in missed optimization opportunities. >Consider the following code. Here the main function for (some reason) computes the square of the total number of arguments twice and returns the sum of the squares.