When is it a good idea to build a new function for an operation?
As in, "for how small of an operation is it worth building a function?" Does it depend on how many times you're going to use it?
Often yes, it's advised that you write a function as soon as you need something more than once. Modern compilers can generally `inline' code -- meaning that they can detect when a function is relatively short and replace the function call with the code in the function itself, thus removing any performance impact from having `too many' function calls. This is, as usual, something you get a feel for, but small functions are not something to be afraid of. If what it does is not particularly evident, you can move a piece of code into a function so that you can give the function a descriptive name and then when it's used the code is clearer.