Comptime Switch | Zig Programming Language | Page 1

teal elm Jul 16, 2023, 7:08 AM

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Is there a way to have a switch that'll only compile the resulting block at comptime? I'm not sure if switch (comptime foo) does this without actually checking the value at execution.

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I guess this is the wrong question to ask, what I'm more looking for is the ability to write this Rust code in Zigrust #[cfg(unix)] fn a() {} #[cfg(windows)] fn a() {}

little arrow Jul 16, 2023, 7:12 AM

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const builtin = @import("builtin");
fn a() {
    if (builtin.os.tag == .windows) {
        // windows specific
    } else {
        // other implementation
    }
}

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if the condition of an if or switch is known at comptime, then only the corresponding prong will be evaluated

teal elm Jul 16, 2023, 7:14 AM

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little arrow if the condition of an `if` or `switch` is known at comptime, then only the corr...

So in this case, would it be preferrable to check the target os rather than the os?

little arrow Jul 16, 2023, 7:14 AM

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I'm not sure what distinction you are making

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builtin.os.tag is the operating system that your program is being compiled to run on

teal elm Jul 16, 2023, 7:15 AM

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What if I select a target, because I plan to cross-compile to Windows and Mac OS.

little arrow Jul 16, 2023, 7:15 AM

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yes, the cross-compile target os

teal elm Jul 16, 2023, 7:16 AM

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I guess I should try it and see!

little arrow Jul 16, 2023, 7:16 AM

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there's no way to know in a program what os it was compiled on

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you could set build options from a build script if you really needed to

teal elm Jul 16, 2023, 7:17 AM

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little arrow there's no way to know in a program what os it was compiled on

I'm unsure what you mean?

little arrow Jul 16, 2023, 7:18 AM

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you can compile the same program that runs on windows from windows, linux, or mac and the program only knows that it was compiled for windows

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and in theory you get the exact same executable in each case

#Comptime Switch