[sidkshatriya]

I like Odin and hope for it to gain more momentum.

I have an important metric for new "systems" languages: does the language allow NULL for it's commonly used pointer type. Rust by default does not (References may _not_ be NULL). Here is where I think Odin makes a mistake.

In the linked blog post Odin mentions ^os.File which means pointer to File (somewhat like *FILE in C). Theoretically the pointer can be NULL. In practice, maybe I would need to check for NULL or maybe I would not (I would have to scan the Odin function's documentation to see what the contract is).

In Rust, if a function returns &File or &mut File or Box<File> etc. I know that it will never be NULL.

So Odin repeats the famous "billion-dollar mistake" (Tony Hoare). Zig in comparison is bit more fussy about NULL in pointers so it wins my vote.

Currently this is my biggest complaint about Odin. While Odin packages a lot of power programming idioms (and feels a bit higher level and ergonomic than Zig) it makes the same mistake that Golang, C and others make regarding allowing NULL in the default pointer type.

[rtpg]

One thing I think worth considering for systems languages on this point: if you don't want to solve every expressiveness issue downstream of Result/Option/etc from the outset, look at Swift, which has nullable types.

MyObject can't be null. MyObject? can be null. Handling nullability as a special thing might help with the billion-dollar mistake without generating pressure to have a fully fleshed out ADT solution and everything downstream of that.

To people who would dismiss ADTs as a hard problem in terms of ergonomics: Rust makes it less miserable thanks to things like the question-mark shorthand and a bazillion trait methods. Languages like Haskell solve it with a monads + do syntax + operating overload galore. Languages like Scala _don't_ solve it for Result/Option in any fun way and thus are miserable on this point IMHO

[tialaramex]

I like to think about how many problems a feature solves to judge whether it's "worth it". I believe that the Sum types solve enough different problems that they're worth it, whereas nullability solves only one problem (the C-style or Java-style null object) the Sum types can solve that with Option<T> and also provide error handling with Result<T, Err> and control flow with ControlFlow<Continue, Break> among others so that's already a better deal.

Nullability is a good retro-fit, like Java's type erased generics, or the DSL technology to cram a reasonable short-distance network protocol onto the existing copper lines for telephones. But in the same way that you probably wouldn't start with type erased generics, or build a new city with copper telephone cables, nullability isn't worth it for a new language IMO.

[noelwelsh]

The Scala solution is the same as Haskell. for comprehensions are the same thing as do notation. The future is probably effect systems, so writing direct style code instead of using monads.

It's interesting that effect system-ish ideas are in Zig and Odin as well. Odin has "context". There was a blog post saying it's basically for passing around a memory allocator (IIRC), which I think is a failure of imagination. Zig's new IO model is essentially pass around the IO implementation. Both capture some of the core ideas of effect systems, without the type system work that make effect systems extensible and more pleasant to use.

[_flux]

I personally don't enjoy the MyObject? typing, because it leads to edge cases where you'd like to have MyObject??, but it's indistinguishable from MyObject?.

E.g. if you have a list finding function that returns X?, then if you give it a list of MyObject?, you don't know if you found a null element or if you found nothing.

It's still obviously way better than having all object types include the null value.

[throwthrowuknow]

Odin’s design is informed by simplicity, performance and joy and I hope it stays that way. Maybe it needs to stay a niche language under one person’s control in order to do so since many people can’t help but try to substitute their own values when touring through a different language.

[gingerBill]

I think the notion that "null" is a billion dollar mistake is well overblown. NULL/nil is just one of many invalid memory addresses, and in practice most of invalid memory address are not NULL. This is related to the drunkard’s search principle (a drunk man looks for his lost keys at night under a lamppost because he can see in that area). I have found that null pointers are usually very easy to find and fix, especially since most platforms reserve the first page of (virtual) memory to check for these errors.

In theory, NULL is still a perfectly valid memory address it is just that we have decided on the convention that NULL is useful for marking a pointer as unset.

Many languages (including Odin) now have support for maybe/option types or nullable types (monads), however I am still not a huge fan of them in practice as I rarely require them in systems-level programming. I know very well this is a "controversial" opinion, but systems-level programming languages deal with memory all the time and can easily get into "unsafe" states on purpose. Restricting this can actually make things like custom allocators very difficult to implement, along with other things.

n.b. Odin's `Maybe(^T)` is identical to `Option<&T>` in Rust in terms of semantics and optimizations.

[01HNNWZ0MV43FF]

It's just weird to defend getting less help from the compiler in a situation where that help is so easy to give.

[sidkshatriya]

> I have found that null pointers are usually very easy to find and fix, especially since most platforms reserve the first page of (virtual) memory to check for these errors.

This is true. However, you have done these fixes after noticing them at runtime. This means that you have solved the null problem for a certain control + data state in code but you don't know where else it might crop up again. In millions of lines of code, this quickly becomes a whack-a-mole.

When you use references in Rust, you statically prove that you cannot have null error in a function for all inputs the function might get if you use Rust style references. This static elimination is helpful. Also you force programmers to distinguish between &T and Option<&T> and Result<&T,E> -- all of which are so common in system's code.

Today it is safe to assume that a byte is 8 bits. Similarly it is safe to assume that the first page in virtual memory is non-readable and non-writable -- why not make use of this fore knowledge ?

> This is related to the drunkard’s search principle (a drunk man looks for his lost keys at night under a lamppost because he can see in that area).

This is a nice example and I do agree in spirit. But then I would offer the following argument: Say, a problem (illegal/bad virtual address) is caused 60% by one culprit (NULL dereference) and 40% by a long tail of culprits (wrong virtual memory address/use after free etc). One can be a purist and say "Hey, using Rust style references" only solves the 60% case, addresses can be bad for so many other reasons ! Or one can pragmatic and try to deal with the 60%.

I cringe every time I see *some_struct in Linux kernel/system code as function argument/return. Does NULL indicate something semantically important ? Do we need to check for NULL in code that consumes this pointer ? All these questions arise every time I see a function signature. Theoretically I need to understand the whole program to truly know whether it is redundant/necessary to check for NULL or not. That is why I like what Rust and Zig do.

[remexre]

> get into "unsafe" states on purpose

see, this seems like something that's nice to actually put into the types; a Ptr<Foo> is a real pointer that all the normal optimizations can be done to, but cannot be null or otherwise invalid, and UnsafePtr makes the compiler keep its distance and allows whatever tricks you want.

[jchw]

I wonder if some day we'll look back differently on the "billion-dollar mistake" thing. The key problem with null references is that it forces you to either check any given reference to see if it's null if you don't already know, or you would have to have a contract that it can't be null. Not having null references really does solve that problem, but still in every day programs you often wind up with situations where you actually can know from the outside that some function will return a non-empty value, but the function itself is unable to make that guarantee in a way that the compiler can enforce it; in those cases, you have no choice but to face the same dilemma. In Rust this situation plays out with `unwrap()`, which in practice most reasonably-sized codebases will end up with some. You could always forbid it, but this is only somewhat of an improvement because in a lot of cases there also isn't anything logical to do once that invariant hasn't held. (Though for critical production workloads, it is probably a good idea to try to find something else to do other than let the program entirely crash in this event, even if it's still potentially an emergency.)

In other words: after all this time, I feel that Tony Hoare framing null references as the billion-dollar mistake may be overselling it at least a little. Making references not nullable by default is an improvement, but the same problem still plays out so as long as you ever have a situation where the type system is insufficient to be able to guarantee the presence of a value you "know" must be there. (And even with formal specifications/proofs, I am not sure we'll ever get to the point where is always feasible to prove.) The only real question is how much of the problem is solved by not having null references, and I think it's less than people acknowledge.

(edit: Of course, it might actually be possible to quantify this, but I wasn't able to find publicly-available data. If any organization were positioned to be able to, I reckon it would probably be Uber, since they've developed and deployed both NullAway (Java) and NilAway (Go). But sadly, I don't think they've actually published any information on the number of NPEs/panics before and after. My guess is that it's split: it probably did help some services significantly reduce production issues, but I bet it's even better at preventing the kinds of bugs that are likely to get caught pre-production even earlier.)

[tialaramex]

I think Hoare is bang on because we know the only similar values in many languages are also problematic even though they're not related to memory.

The NaNs are, as their name indicates, not numbers. So the fact this 32-bit floating point value parameter might be NaN, which isn't even a number, is as unhelpful as finding that the Goose you were passed as a parameter is null (ie not actually a Goose at all)

There's a good chance you've run into at least one bug where oops, that's NaN and now the NaN has spread and everything is ruined.

The IEEE NaNs are baked into the hardware everybody uses, so we'll find it harder to break away from this situation than for the Billion Dollar Mistake, but it's clearly not a coincidence that this type problem occurs for other types, so I'd say Hoare was right on the money and that we're finally moving in the correct direction.

[grumpyprole]

It's overblown until it isn't. Hoare didn't pluck that number from thin air. This is now a solved problem in modern programming languages. If Odin doesn't have this and other essential memory safety features, it's certainly not worth the massive retooling effort.

[leecommamichael]

Odin offers a Maybe(T) type which might satisfy your itch. It's sort of a compromise. Odin uses multiple-returns with a boolean "ok" value for binary failure-detection. There is actually quite a lot of syntax support for these "optional-ok" situations in Odin, and that's plenty for me. I appreciate the simplicity of handling these things as plain values. I see an argument for moving some of this into the type-system (using Maybe) when it comes to package/API boundaries, but in practice I haven't chosen to use it in Odin.

[sidkshatriya]

All the standard libraries use naked ^T .

Maybe(T) would be for my own internal code. I would need to wrap/unwrap Maybe at all interfaces with external code.

In my view a huge value addition from plain C to Zig/Rust has been eliminating NULL pointer possibility in default pointer type. Odin makes the same mistake as Golang did. It's not excusable IMHO in such a new language.

[phplovesong]

Not a Odin user, but iirc odin also has Go like zero values. There is no practical option unless you have null. Like a string cant be null, its "at least" an empty string. But whats a base value for a pointer? A function? An interface? Either you wrap (ocaml style) or use null. Its pragmatism vs correctness, a balance as old as computing.

[gingerBill]

Odin's type system is just different to many other languages, and trying to compare it to others doesn't always work out very well.

`Maybe` does exist in Odin. So if you want a `nil` string either use `Maybe(string)` or `cstring` (which has both `nil` (since it is a pointer) and `""` which is the empty string, a non-nil pointer). Also, Odin doesn't have "interface"s since it's a strictly imperative procedural language.

As for you question about base values, I am not sure what you mean by this. Odin hasn't got a "everything is a pointer internally" approach like many GC'd languages. Odin follows in the C tradition, so the "base value" is just whatever the type is.