undefined | Better HN

0 pointsAndyKelley3y ago0 comments

    // compile-time initialized mutable global:
    var foo = bar();

0 comments

5 comments · 2 top-level

kllrnohj3y ago· 2 in thread

> If a container level variable is const then its value is comptime-known, otherwise it is runtime-known.

I'm not sure how to reconcile that Zig documentation with your comment's claim. It appears that Zig relies on opportunistic behaviors here instead of contracts. That is, your var foo could be comptime known, but isn't required to be. Which is fine enough, but not comparable to `constinit` either.

Alternatively if all container variables are exclusively comptime initialized, then the obvious missing part from Zig would be the inverse of constinit which is the onload initializer behavior.

anonymoushn3y ago

The quoted documentation says if you initialize a mutable variable to 5 at compile time and later change it to 2 and print it, it won't print 5, because uses of that variable in expressions won't be resolved to the constant value used to initialize it at compile time.

When is onload? I don't think that's a time that occurs during program execution in Zig.

kllrnohj3y ago

Does Zig not have an equivalent of `__attribute__((constructor))`?

If not then that'd be the 3rd type of initialization it's missing, the equivalent of C++'s nothing specified.

1 more reply

lvass3y ago· 1 in thread

How does one assert bar() or better yet, an arbitrary expression you place there, is pure?

anonymoushn3y ago

Well, the compiler attempts to evaluate bar(), and if it cannot, you get a compile error

j / k navigate · click thread line to collapse

0 comments

5 comments · 2 top-level

kllrnohj3y ago· 2 in thread

> If a container level variable is const then its value is comptime-known, otherwise it is runtime-known.

I'm not sure how to reconcile that Zig documentation with your comment's claim. It appears that Zig relies on opportunistic behaviors here instead of contracts. That is, your var foo could be comptime known, but isn't required to be. Which is fine enough, but not comparable to `constinit` either.

Alternatively if all container variables are exclusively comptime initialized, then the obvious missing part from Zig would be the inverse of constinit which is the onload initializer behavior.

anonymoushn3y ago

The quoted documentation says if you initialize a mutable variable to 5 at compile time and later change it to 2 and print it, it won't print 5, because uses of that variable in expressions won't be resolved to the constant value used to initialize it at compile time.

When is onload? I don't think that's a time that occurs during program execution in Zig.

kllrnohj3y ago

Does Zig not have an equivalent of `__attribute__((constructor))`?

If not then that'd be the 3rd type of initialization it's missing, the equivalent of C++'s nothing specified.

1 more reply

lvass3y ago· 1 in thread

How does one assert bar() or better yet, an arbitrary expression you place there, is pure?

anonymoushn3y ago

Well, the compiler attempts to evaluate bar(), and if it cannot, you get a compile error

j / k navigate · click thread line to collapse