bux-lang/examples/is_operator.bux

// is_operator.bux — `expr is Variant` for simple and algebraic enums
import Std::Io::{PrintLine, PrintInt};

enum Color {
    Red,
    Green,
    Blue,
}

enum Box {
    Val(int),
    Empty,
}

func Main() -> int {
    let c: Color = Color { tag: Color_Red };
    if c is Red {
        PrintLine("color-red");
    }
    if c is Blue {
        PrintLine("color-blue-unexpected");
    } else {
        PrintLine("color-not-blue");
    }

    let b: Box = Box { tag: Box_Val };
    b.data.Val_0 = 42;
    if b is Val {
        Print("box-val=");
        PrintInt(b.data.Val_0 as int64);
        PrintLine("");
    }
    if b is Empty {
        PrintLine("box-empty-unexpected");
    } else {
        PrintLine("box-not-empty");
    }

    return 0;
}