by pron | 2025-11-08 00:03:08+00:00
> I can’t think of any other language in my 45 years long career that surprised more than Zig.

I can say the same (although my career spans only 30 years), or, more accurately, that it's one of the few languages that surprised me most.

Coming to it from a language design perspective, what surprised me is just how far partial evaluation can be taken. While strictly weaker than AST macros in expressive power (macros are "referentially opaque" and therefore more powerful than a referentially transparent partial evaluation - e.g. partial evaluation has no access to an argument's name), it turns out that it's powerful enough to replace not only most "reasonable" uses of macros, but also generics and interfaces. What gives Zig's partial evaluation (comptime) this power is its access to reflection.

Even when combined with reflection, partial evaluation is more pleasurable to work with than macros. In fact, to understand the program's semantics, partial evaluation can be ignored altogether (as it doesn't affect the meaning of computations). I.e. the semantics of a Zig program are the same as if it were interpreted by some language Zig' that is able to run all of Zig's partial-evaluation code (comptime) at runtime rather than at compile time.

Since it also removes the need for other specialised features (generics, interfaces) - even at the cost of an aesthetic that may not appeal to fans of those specialised features - it ends up creating a very expressive, yet surprisingly simple and easy-to-understand language (Lisps are also simple and expressive, but the use of macros makes understanding a Lisp program less easy).

Being simple and easy to understand makes code reviews easier, which may have a positive impact on correctness. The simplicity can also reduce compilation time, which may also have a positive impact on correctness.

Zig's insistence on explicitness - no overloading, no hidden control flow - which also assists reviews, may not be appropriate for a high-level language, but it's a great fit for an unabashedly low-level language, where being able to see every operation as explicit code "on the page" is important. While its designer may or may not admit this, I think Zig abandons C++'s belief that programs of all sizes and kinds will be written in the same language (hence its "zero-cost abstractions", made to give the illusion of a high-level language without its actual high-level abstraction). Developers writing low-level code lose the explicitness they need for review, while those writing high-level programs don't actually gain the level of abstraction required for a smooth program evolution that they need. That belief may have been reasonable in the eighties, but I think it has since been convincingly disproved.

Some Zig decisions surprised me in a way that made me go more "huh" than "wow", such as it having little encapsulation to speak of. In a high-level language I wouldn't have that (after years of experience with Java's wide ecosystem of libraries, we learned that we need even more and stronger encapsulation than we originally had to keep compatibility while evolving code). But perhaps this is the right choice for a low-level language where programs are expected to be smaller and with fewer dependencies (certainly shallower dependency graphs). I'm curious to see how this pans out.

Zig's terrific support for arenas also makes one of the most powerful low-level memory management techniques (that, like a tracing garbage collector, gives the developer a knob to trade off RAM usage for CPU) very accessible.

I have no idea or prediction on whether Zig will become popular, but it's certainly fascinating. And, being so remarkably easy to learn (especially if you're familiar with low-level programming), it costs little effort to give it a try.