# Finish before you Start

I find a lot of the coding I do is completely different, unlike anything I’ve done before. The reason is that if it’s anything like something I’ve done before then I’ve failed to recognize the pattern and abstract it out. As a software engineer I want to never be doing repetitive tasks, because that’s what software is for (repeating tasks). If you’re repeating yourself in any way then you’re not fully leveraging your time. Every pattern, every similarity, every “oh, I know how to do this because I did something similar with xyz” should be under careful scrutiny.

After a certain point you may run up against the limitations of a programming language, since many design patterns are simply language features that are missing. I come across this all the time in embedded C programming, where a “linked list” is not a container but the design pattern of having a next pointer in a structure (and all the algorithms that go with it), and a “virtual class” is not a data type but the pattern having a vtable pointer at the beginning of a structure.

At the point where the language betrays you, your next port of call could be writing your own domain specific language to target the problems you’re working on. In C# this may include the use of reflection to interpret existing C# data structures in new ways (such as interpreting a class as a list of serializable members), using expression trees to interpret C# expressions in new ways, or using reflection.emit to dynamically generate bytecode.

But despite the huge advantages of automating the mundane programming tasks and patterns, the problem arises: if you never repeat yourself, then everything is new. Everything is uncharted territory1. How do you know how long it will take? How do you know if it will work? Will it really be useful?

The solution is simple: finish before you start. Do whatever it takes to get the results of your experimentation before you actually perform the experiment. In software this means developing proof of concepts. Hack the result together using whatever means necessary. Spare no time for optimization or good coding technique. Don’t worry about corner cases and details. Get to the finish line by cutting across the sports field. Get to the finish line by cheating. By redefining the race. By faking the results. Calculate them manually. Hand-draw the GUI. Fake the input data. Brute-force the algorithm. Anything it takes.

It helps to clearly define the interface of whatever you’re coding: How will it interact with the rest of the system? If it’s a web page, the interface is the GUI. If it’s a library, the interface is the publicly exposed API. If it’s a DSL, the interface is a syntax or spec. Once the interface is there, it doesn’t matter if implementation is a birds-nest of cheating and killing. All that matters is that the interface offers just – just – enough to give you a little hint of what the future will look like. What it will feel like? Get a tangible product you can play with2.

Once you’ve seen the end, then you can start. A clearer picture of where you’re going will help not only in producing a better product or code, but it might change your direction completely. Once your fortune is told, it may bring news of triumph, or of peril. Perhaps when you see the end you realize it actually isn’t so great there. It isn’t as easy to use as you thought. It’s more complicated than anticipated. Perhaps the whole principle is flawed in some horrible way. There are many things that are hard to anticipate without getting a closer look. Or a hands-on experience. Perhaps you need to reconsider some of your assumptions, or abandon the whole idea altogether.

It’s better to know before you start.

1. This is an exaggeration and oversimplification

2. I use the word “tangible” very loosely. A visual interface is “tangible” if you can see it, and a library interface is tangible if you can call it, etc.

## One thought on “Finish before you Start”

1. Chithralekha says:

I am a big fan of ‘Mock objects’ in Object Oriented Programming.