Avoid Negations

Has anyone ever told you to “think positively”? Turns out, positive expressions are better in your code than negative ones because they’re often easier to grasp and they take up slightly less space.

The problem code shown here is another variant of the Laboratory component. It provides two methods that take a Sample and return a Result. There’s nothing obviously wrong with the code. It’ll fulfill its purpose, but it’s more complex than necessary.

Consider the conditions of the if statements: Both express a negating condition. The first one tests if a sample isInorganic(). The second one even uses the Boolean operator for negation: the exclamation mark ’!’.

In most cases, you’ll find it easier to understand positive expressions when you read code. A negated expression adds one extra layer of indirection. Instead of a simple “X does apply,” you have to grasp an additional token: “X does not apply.”

This extra token is often unnecessary. Although it seems like a minor change, every tiny bit of simplification helps for more complex expressions (those that you’ll find in real code).

Remember: Everybody likes no negations.

Now, take a look at the simplified version:

We changed the code only slightly, but that already has an effect. Instead of isInorganic(), we’re calling isOrganic(), which has a positive wording instead of a negative one. That is, we have to switch the bodies of the if and else blocks.

When it comes to the second part, we’re calling the same method, isHumanoid(), but we eliminated the negation. This is a real simplification of the code. Again, it means that we have to switch the bodies of the if and else blocks.

All in all, these changes are quite simple and you might wonder: why should I bother? You should bother because it improves the understandability of the code and comes at virtually no cost. You don’t usually have to add further lines of code. All you have to do is re-sort existing parts of the code and you’ll see an improvement. It’s an opportunity that’s too good to let go!

Sometimes, however, you need the appropriate methods, like the isOrganic() instead of isInorganic() here. If the code you’re calling comes from a third-party library, you might not have the option to invoke different methods. But when you control it, don’t shy away from adding that method to the appropriate class—the few lines of code are worth their characters, because they make your code clearer in other places. In the long run you’ll end up with less code, since such methods reduce code duplication and can be reused in other parts of the program. From our experience, it’s best to get rid of the negative method completely—no need to maintain two similar methods.