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> I think it's more likely that Zig will allow user-defined infix operators (say +' or something) before it allows overloading of any kind.

I proposed this and it got rejected by the language committee.

I meant that they'd sooner allow some infix operators than overloading, not that they intend to add operators in the language's first version.

> because overloading introduces ambiguity that cannot be resolved at the code-unit level

Can you explain this a bit? Operator overloading just seems like such a strange bugbear of Zig folks to me. Maybe I've just never been bitten by it, but at least in Elixir, my main language, I've never really understood the danger.

Are operators truly so different from functions? You'd expect that any function you import could do, well, anything. Aren't operators essentially just the same thing, just with a "prelude" in the language that basically imports them by default?

In Elixir, you might have (discouraged):

    defmodule MyMod do
      import MyOperators

and then you know to check what's defined by MyOperators, for that module. But more common, if you really wanted to overload, would be to be more specific:

    defmodule MyMod do
      import MyOps, only: [+: 2]

and then you know plus (with two arguments) has a different meaning in that module.

I’m not super familiar with Zig specifically, aside from watching some of Andrew’s talks and coding streams. But this thought process is not a Zig only concept. As far as I know, the explicit ‘operators’ that are provided with Zig are guaranteed to be a low-level construct (ideally implemented at the ISA level) which are made visible to users of the language in standard ways, i.e. infix arithmetic operators. When overloading of these operators is allowable that guarantee goes out the window. There is a fundamental difference at the generated code level between a function call resulting from a use of ‘’ to multiple two random matrices and a use of ‘’ to multiple two 32 but integers. Further, as I understand it, Zig guarantees that anything that allocates memory does so explicitly and anything that calls a function does so explicitly. The very concept of operator overloading is incompatible with such a guarantee. So, I think given the implied goal of explicit is better, it makes sense that a flat rejection of operator overloading is the broad view.

So zig doesn't support 64bit arithmetics on 32/16/8bit architectures? What about division? Quite a few hardware don't support division( https://community.arm.com/developer/ip-products/processors/b...).

> The very concept of operator overloading is incompatible with such a guarantee.

Why would operator overloading allocate memory? The memory is already allocated(by the user) when you call with the operands.

> Why would operator overloading allocate memory?

What if I wanted to overload the + operator to concatenate strings?

Yes that was poorly thought out. I realized it after i commented.

There is definitely some merit in being puritanical about not having any allocations in operators.

> Operator overloading just seems like such a strange bugbear of Zig folks to me.

Not operator overloading; just overloading. You can't overload ordinary-named subroutines in Zig either.

> and then you know plus (with two arguments) has a different meaning in that module.

That's not overloading, that's shadowing. Overloading is when the same name refers to multiple things depending on the type of its arguments. Erlang allows overloading based on arity, but that's something that can be understood from the call-site code.

> overloading introduces ambiguity that cannot be resolved at the code-unit level

This seems clearly false to me. Operator overloading is non-virtual type-based dispatch, just like the dot operator for method calls in C++/Java/etc., and is resolved statically at compile time. You can think of overloadable "+" as just syntactic sugar for an ".add()" method (in fact, this is more or less exactly how it's implemented in Rust). Even if your language doesn't have methods, you can implement overloading with typeclasses, like Haskell does (as does Rust, formally speaking).

Operators are a red herring here; what Zig disallows is overloading of names, period. Yes, overloading is resolved statically at compile time, but that's not the point (Zig does allow dynamic dispatch). The point is that a simple understanding of what the code does requires information available outside the unit (subroutine or even file). A subroutine can contain two references to `foo` resolving to two different targets, but you can't know that from the code in the subroutine. The meaning of a name must be defined in one place in Zig, and a name can only refer to one thing.

We could certainly argue on whether disallowing overloading is helpful, but it's first important to understand what the principle is, and it's not about the operators.

> The point is that a simple understanding of what the code does requires information available outside the unit (subroutine or even file).

No, it doesn't. Knowing what function "+" resolves to requires only the type of the left-hand side (or, I think, the RHS as well in Haskell). Absent overlapping instances (which Rust doesn't support, and Haskell only supports with an extension), there can only be one such function implementation per type. And, since top-level items are fully type-annotated in Rust (and idiomatically annotated in Haskell), this is a completely local determination. Therefore, for every occurrence of "+" in the source, it's completely unambiguous which implementation "+" calls, and this can be determined solely by looking at the calling function.

The end result: Rust, like Zig, disallows overloading of names, but Rust also effectively supports overloaded operators via traits (typeclasses).

> there can only be one such function implementation per type

Right, and that's more than one definition per name. In Zig, a name refers to only one definition. (Plus, recall that in Zig the type of a target isn't always known when reading the code, probably more frequently than in C++ or Rust, where this only happens in macros.)

> disallows overloading of names

That the definition referred to by an identifier depends on the type is what overloading means. Overloading is the very essence of traits.

P.S.

> in C++ or Rust, where this only happens in macros

Sorry, this is wrong. In both of these languages it happens much more frequently. All the time, in fact, whenever you either infer return types or just chain calls on return values, or when the type is a generic/template type parameter. So when you see `foo(e)` or `e.foo()`, where `e` is some expression, you can only tell which definition of `foo` is referenced -- or even whether two instances of `foo` refer to the same definition or not -- by figuring out the type of `e`, which is often implicit in the code.

> Overloading is the very essence of traits.

Which is why in Zig, the mechanisms that perform a similar task to that of traits -- i.e. abstracting over types -- work differently, without overloading.

As a general rule, Zig does not want the semantics of a piece of code to depend on things the compiler might know but the reader of the unit might not. Whether or not such a degree of explicitness is a worthy principle for a low-level language is a matter of taste, I suppose.