Macros can use + in the argument list to indicate that an argument may
repeat at least once, or *, to indicate that the argument may repeat zero or
more times.
In the following example, surrounding the matcher with $(...),+ will
match one or more expression, separated by commas.
Also note that the semicolon is optional on the last case.
// `min!` will calculate the minimum of any number of arguments.
macro_rules! find_min {
// Base case:
($x:expr) => ($x);
// `$x` followed by at least one `$y,`
($x:expr, $($y:expr),+) => (
// Call `find_min!` on the tail `$y`
std::cmp::min($x, find_min!($($y),+))
)
}
fn main() {
println!("{}", find_min!(1u32));
println!("{}", find_min!(1u32 + 2 , 2u32));
println!("{}", find_min!(5u32, 2u32 * 3, 4u32));
}