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zig

How to write `fn UInt(bit_size) type` such that UInt(24) returns u24?

To my understanding, Zig supports types u1..u65535.

How would I need to implement fn U(comptime bitsize: u16) type such that U(n) == un for u in 1..65535?

Or is there a builtin way to do that?

I'm trying to do something like:

union (enum(u4)) {
  a: void,
  ...
  x: U(32-4),
  y: I(32-4),
  z: C((32-4/8))
}

For example: A tagged union with a total size of 32 bits where X bits are used for tag values and the remaining bits for data.

Solution

  • You can use @Type to achieve this:

    fn UInt(comptime bitsize: u16) type {
    return @Type(.{ .Int = .{ .signedness = .unsigned, .bits = bitsize } });
}

pub fn main() !void {
    const x: UInt(32-4) = 0;
    @compileLog(@TypeOf(x));
}

    This prints:

    Compile Log Output:
@as(type, u28)