kleene start

Chapter09/metaprogramming_ebnf.rs

@@ -15,6 +15,12 @@ macro_rules! abc_or_aaa {
   (a a a) => { println!("'a a a' is also correct syntax.") };
 }
 
+//this is a grammar sequence matching many of one token
+macro_rules! many_a {
+  ( $($a:ident)* ) => {{ $( print!("one {} ", stringify!($a)); )* println!(""); }};
+  ( $($a:ident),* ) => {{ $( print!("one {} comma ", stringify!($a)); )* println!(""); }};
+}
+
 fn main() {
    abc!(a b c);
 
@@ -23,4 +29,7 @@ fn main() {
 
    abc_or_aaa!(a b c);
    abc_or_aaa!(a a a);
+
+   many_a!(a a a);
+   many_a!(a, a, a);
 }