Expression

The idea is to express the instructions to the computer that you’ve crafted in a succinct but entirely verifiable way.

If the expression is huge, the size itself will cripple your ability to verify that the instructions are correct.

If the expression is shrunk with cryptic syntax, maybe when you write it you will remember how it works, but as time goes by that knowledge fades and it will cripple your ability to verify that it is correct.

If the expression is fragmented all over the place, the lack of locality will cripple your ability to verify that it is correct.

Spaghetti code or scrambled structure is the same. Same with globals, bad names, poor formatting, etc. You can’t just look at it and mostly know that it will do what it needs to do. Obviously, this type of visual verification saves a huge amount of time debugging but it also tends to prevent a lot of mistakes in the first place.

Hiding the way things work is usually not a problem with a small amount of code. It's the small size that makes it absorbable, so you can verify it. But as the size grows, little mistakes have much larger consequences. A badly written medium-sized system is tricky to debug, but for large and huge systems it verges on impossible. Small mistakes in code organization can eat through big chunks of time. Splatter coding techniques may seem fun, but they are a guaranteed recipe for poor quality.

Getting the right degree of readability in code takes a careful balancing of all aspects of expression. Naming, logic, structure, and a lot of other issues. If you see good code, it isn’t always obvious how much work went into rearranging it to make it simple and clear, but it certainly wasn’t just chucked out in a few minutes. The authors spent quite a bit of effort on clarity and readability. They pay close attention to the details, in that way, it is not dissimilar to writing big articles or books. Careful editing is very important.

The quality of code is closely related to the diligence and care applied by the author. You think clearly about how to really solve the problem, then your code as cleanly as you can for each of the moving parts, and then you relentlessly edit it over and over again until it is ready to go. That is the recipe for good code.