Hacker News Reader

Comment by logimame | Hacker News Reader

D, Nim, and Haxe had it for quite some time (Along with Jai, which is yet unreleased to the public), although you can argue that Zig’s implementation is conceptually the simplest (it has merged compile time semantics with generic types in a unified way).

View on HN

One subtle but extremely important feature of Zig's comptime is that is emulates the target architecture. Fundamental for implementing correct cross compilation.

That's pretty impressive. It's always annoying to get bit struct alignment issues. :/

Zig's revolution is not in adding a partial evaluation feature, but in removing many other separate features that can be expressed as mere applications. As Antoine de Saint-Exupery said, "Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away."

And Lisp since even a much longer time.

I see some abstract aesthetic similarities between Zig and Lisp, or some Lisp's at least -- especially their minimalism -- but Zig's partial evaluation (comptime) works nothing at all like Lisp's syntactic macros (there is no quoting construct, and you don't manipulate syntactic terms at all), and, in fact, has much simpler semantics. The result is intentionally weaker than macros -- macros are "referentially opaque" while comptime is transparent[1] -- but Zig's realisation is that you don't need macros -- with their complexities and pitfalls -- to deliver everything a low-level language would need.

[1]: I.e. if x and y have the same meaning ("reference"), in Lisp -- and in any other language with macros -- you could write a parameterised expression e, such that e(x) does not have the same meaning as e(y); you can't do that in Zig.

Thanks. I'm not familiar with Zig. I responded to the "arbitrary compile-time execution" by adding Lisp to the proposed list of D, Nim, and Haxe. Also the latter might raise some concerns when looking at details as you did with Lisp.

For instance, even if x and y have the same meaning, (let (x) ...) and (let (y) ... ) will not. So if you can't do that in Zig, that implies you can't write a custom binding construct.

A let expression isn't parameterised by x and y but binds their meaning, and the bound variable isn't free in the expression, and you can't substitute it at all. A simple example is an expression that prints the syntactic name of its argument. You can do that in C, C++, Lisp and Rust, but not in Zig (this is OK, because Zig obviates the need for that with excellent backtraces). But this means that you can understand all Zig code as simple Zig code, and that there is no complex meta-language with super-powers as there is in all those other languages I mentioned.

Reply on news.ycombinator.com