On Tue, Apr 09, 2013 at 10:07:36PM -0400, Ashish Myles wrote:
> Hi,
>
> I am running the rust compiler from trunk. My macro usage seems to be a
>
> ----
> macro_rules! my_print(
> ($a:expr, $b:expr) => (
> io::println(fmt!("%d", a));
> io::println(fmt!("%d", b));
> );
> )
>
> fn main() {
> let a : int = 1;
> let b : int = 2;
> my_print!(a, b);
> }
> ----
>
> Compiling with "rustc tmp.rs" gives the following suspicious warning
>
> ----
> tmp.rs:10:8: 10:11 warning: unused variable: `b`
> tmp.rs:10 let b : int = 2;
> ----
>
> and ./tmp prints only "1". Running "rustc tmp.rs --pretty expanded"
> shows below that the second line "io::println(fmt!("%d", b));" was
> ignored.
>
> ----
> fn main() {
> let a: int = 1;
> let b: int = 2;
> io::println({
> let mut __fmtbuf = ~"";
>
> ::unstable::extfmt::rt::conv_int(::unstable::extfmt::rt::Conv{flags:
>
> ::unstable::extfmt::rt::flag_none,
>
> width:
>
> ::unstable::extfmt::rt::CountImplied,
>
> precision:
>
> ::unstable::extfmt::rt::CountImplied,
>
> ty:
>
> ::unstable::extfmt::rt::TyDefault,},
> a, &mut __fmtbuf);
> __fmtbuf
> });
> }
> ----
>
> Can someone point me in the right direction here?
Currently, macros can only expand to a single item. See
https://github.com/mozilla/rust/issues/4375 for more details.
-doy
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