I wasn't born in Yorkshire, but I spent most of my childhood growing up there. Yorkshire, a large county in the north east of England, has its own collection of slang, not least including the word "aye", which it appears is appropriate in response to pretty much any situation. Another slang phrase is "divvy up". Basically, this just means to divide a bunch of things up somehow.
These days, I spend a lot of my time writing C#. If I'm dealing with a bunch of things in C#, I'll usually store them in a generic List collection, or some other collection. This got me thinking: how can I divvy up a List in C# into multiple Lists? And that's when I decided to implement the Divvy extension method.
What we're aiming for
Suppose we have a list of scores:
var Scores = new List<int>()
{ 87, 32, 45, 60, 91, 10, 58, 77, 66, 71 };...
Higher Order Programming is one of those things that to many people sounds weird, magical, mysterious or just too hard for them to be able to do. It's not. If you have ever passed a function or method as a parameter to another function or method, then you have done higher order programming. If you have ever used a function pointer in C or a delegate in C# or some kind of callback mechanism, then you have done higher order programming.
Define it!
We are all used to writing code that takes parameters. We do it whenever we write subroutines, functions or methods. Normally these parameters are data. In higher order programming, one or more of these parameters is code rather than data. That is, you can pass code, functions and/or methods around, just as you can pass data around. That's all there is to it.
Show me an example
Let's look at C#, because the syntax will not be too unusual to programmers in many languages. Suppose we have a List of scores for a test...
Most programmers today will be familiar with a number of programming paradigms. The age-old procedural programming paradigm, where a program is broken down into a number of procedures or routines, is still very much alive and the right solution for a number of problems. Object Oriented programming is one of the most popular and fashionable paradigms today, allowing for a good level of code re-use through mechanisms such as instance management (one class can be instantiated many times to give many objects), data hiding (think private variables in a class) and inheritance.
Another paradigm cross-cuts these two: that of imperative programming. This simply means that a program consists of a sequence of instructions that are executed one after the other (or at least appear to be; both the compiler and the CPU may well re-order instructions to improve performance when it does not affect the behavior of the program). In fact, when I was younger my definition of a computer program included the words “a sequence of instructions”...
