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The Happy Path

Every movement needs an enemy, it galvanises followers, gives a community a sense of some shared identity. Even if Group A aspire to nothing more than to not be like Group B that is at least something to rally around.

“The Waterfall” is increasingly becoming an Alamo for those who aren’t or don’t want to be convinced by talk of “Agile”.

For the Agile community the designated enemy seems to be “The Waterfall Model” and the command and control project management techniques that usually go hand in hand with it.

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Don't Scatter Logic All Over The Call Stack

Here’s a problem I come across all the time in legacy code and I have been guilty of it myself in the past. This isn’t going to be rocket science, but, apparently, this stuff doesn’t go without saying. Normal caveats about this being a simplified contrived example apply.

Take a look at this code

static void Main(string[] args)
{
    PrintTradeBalance();
    Console.ReadKey();
}

Oh! to have code this simple right? It’s pretty clear what it does, it prints a trade balance, whatever that is. Let’s not break out the bunting and brass band yet. What does this code ACTUALLY do. Let’s dig into the function.

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Simplicity

Ladies and Gentlemen of the class of ‘14

If I could offer you only one tip for the future, simplicity would be it. The long term benefits of simplicity have been proven by Rich Hickey whereas the rest of my advice has no basis more reliable than my own meandering experience. I will dispense this advice now.

Beware the over engineered complexity of your code; oh nevermind; you will not understand the over engineered complexity of your code until it bites you in the ass. But trust me, in 2 years you’ll look back at code you’ve written and recall in a way you can’t grasp now how much unnecessary gold plating you added and how little it really achieved.

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Memoization

Imagine you have a long running function that you’d like to avoid running unnecessarily. For the purposes of this post you’ll have to suspend disbelief and pretend that negating a number is an expensive task. This example prints out a message so you can see when it actually gets called.

let Negate n =
    printfn "Negating '%A' this is hard work" n
    -n
 
val Negate : int -> int

> Negate 5;;
Negating '5' this is hard work
val it : int = -5

Now, let’s use that function when writing another. This function takes two numbers, negates the first, then adds the second.

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When Can You Start?

He sat in the large bay window observing the potential candidates as they approached the house. His mind was made up about each of them before they rang the bell.

“I’m here about the gardener job”

“Sorry, the position is filled.”

“Already? OK, thanks, bye”

Again and again all the same. No good. Then…aha! this one.

“I’m here about the gardener job”

“When can you start?”

“You don’t want to ask me any questions?”

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C# Is Too Damn Noisy

I am growing increasingly frustrated with C#. I think the reason for that may be my exposure to languages like F#. In many ways my feelings for C# are quite similar to feelings I had about VB.Net when I was first exposed to C#.

It’s taken me a while to figure out what it is that I find irritating about C# and I think I’m ready to call it. The problem with C# is exactly the same problem I had with VB.Net, it’s too damn noisy.

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Why Do Cars Have Breaks?

Why do cars have brakes?

I noticed this question on Jon Jagger’s blog and I was delighted with myself that I managed to get the “right” answer without peeking.

Stop reading right now, have a think about it, then head on over to Jon’s blog to see what he has to say on the topic.

Then, if you want, read on…

How would you drive if your car didn’t have brakes? Perhaps you’d stick to 5mph because at that speed you can use the wall of the building you’re visiting, or a nearby tree to stop. On a school run 5mph is probably a safe speed at which to throw an average 8 year old from a moving car. Maybe 10mph if they are sturdy.

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Unfolding Sequences

In my last post I worked through an example that finds the range of numbers that sum to a target value, or gets as close as possible without exceeding the target. I mentioned that the solution felt a little too like the loopy code I would have written in non-functional languages. I felt that there might be a more “functional” way of solving the problem, but I didn’t know what it was.

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Iterating, Incrementing, and Accumulating

Another F# session this evening and some more deliberate practice of Functional Thinking. To be fair, this post isn’t really about anything new. If you’ve ever used recursion, even in non-functional languages, this will be old news. If you are new to Functional Programming and/or recursion then this may be useful.

Here’s a really simple function. It accepts a number n and sums all the numbers from 1 to n.

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Partial Application

Warning, novice functional thinker here. If you know your stuff, what follows may cause distress.

I was messing with F# last night and I got a gentle reminder that I’m still a long way from thinking functionally, it still takes a lot of effort.

I started with this

let evens r = List.filter (fun x -> x % 2 = 0) r
> evens [0..10];;

val it : int list = [0; 2; 4; 6; 8; 10]

Simple enough. Even numbers are multiples of 2. Rekindling childhood memories of typing code from books by Tim Hartnell into a ZX81, I did what I would have done then. I tried to make the code do something slightly more complicated. What about a function that can find multiples of any number, not just 2.

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