Hacker News Reader

Comment by magicalhippo | Hacker News Reader

Right, but my point is, the code which would raise an error because the pointer is nil now raises an error because the Optional is not set.

Is there really that much of a difference between those cases?

I agree though that in an interface, Optional conveys a more explicit meaning than something pointer-like, which is always a good thing.

View on HN

In practice it does make a big difference because if the type system knows about it then it can enforce handling of the exception. (Or more generally, it can just force you to pattern match on the optional time and make sure you handle the empty case.)

Go programs crash at runtime. In general, program failures and bugs should surface as soon as possible. Ideally no later than compile time. Instead, Go makes you wait until the app is running.

For an app that has a lot of configuration options, for example, there can be a latent bug that crashes the binary for some options. And that bug may not be detected for months because nobody was using that combination of config options.

The only real defense of this is to pepper your code with a bunch of nil checks. But these nil checks are also hard to test, so Go devs just learn to ignore missing code coverage. In fact, your code coverage metrics look better if you don't check for nil.

I'm sure at some point Go or a library will offer a version of optional types that is well-adopted. But my point is that by the time Go was designed, null references were already widely considered a bad idea and the source of a huge class of computer bugs. Go still deliberately designed them into the type system.

Some people think Optional/Either/etc are the absolute cure to a certain sort of problems and -- I speak from experience -- it is impossible to convince them that it's not.

Well, of course, if your end users, the business users, are okay if you present them an "optional result" which might or might not be a result, then Optionals/Either _are_ the cure. Unfortunately most end users are pissed if you tell them that you optionally shipped their purchase or that the refund will either be credited to their CC or not.

It's about handling those error cases or failing the build, rather than getting a null pointer exception at runtime that moves execution to some higher part that has no context and little ability to correct the problem, or just crashes. You can still handle it wrong, but you are forced to handle it rather than just, in your example, charging the card and crashing the thread when updating the database that you charged them.

One has to be addressed at compile time and the other is a runtime error. Sure, you can address it wrong, but it's better than any reference anywhere being able to throw and in my experience really does cut down on application crashes.

Interesting. I've been coding in languages which heavily rely on pointers for decades, primarily C, C++, C# and Turbo Pascal/Delphi, and in my experience nil pointer errors are quite rare.

I agree that it's nice to be explicit about optional stuff, but overall it's not been a huge deal in the projects I've been involved with.

Reply on news.ycombinator.com