macro_rules! with_float_width {
(kernel $w:expr, $t:ident => $body:expr) => { ... };
($w:expr, $t:ident => $body:expr) => { ... };
}macro_rules! with_float_width {
(kernel $w:expr, $t:ident => $body:expr) => { ... };
($w:expr, $t:ident => $body:expr) => { ... };
}