bux-lang/examples/macro_twice.bux

// Declarative macro! + built-in quote! (session 59)
// Expands before type-check; $frags splice with call-site hygiene.
import Std::Io::{PrintLine};
import Std::String::{String_FromInt};

macro! twice {
    ($x:expr) => {
        ($x) + ($x)
    }
}

macro! add2 {
    ($a:expr, $b:expr) => {
        ($a) + ($b)
    }
}

func Main() -> int {
    let a: int = twice!(21);
    let b: int = add2!(10, 32);
    // quote! is a built-in identity expand (call-site graft)
    let c: int = quote!(a + 1);
    PrintLine(String_FromInt(a));
    PrintLine(String_FromInt(b));
    PrintLine(String_FromInt(c));
    if a != 42 {
        PrintLine("FAIL twice");
        return 1;
    }
    if b != 42 {
        PrintLine("FAIL add2");
        return 1;
    }
    if c != 43 {
        PrintLine("FAIL quote");
        return 1;
    }
    PrintLine("PASS macro_twice");
    return 0;
}