preliminary bang syntax

examples/make_counter.puyo

@@ -0,0 +1,24 @@
+fn make_counter([] [inc]) (
+    i := 0;
+    
+    fn ^inc([] [i]) (
+        i := i + 1;
+        ^i := i;
+    );
+);
+
+a := make_counter!;
+b := make_counter!;
+
+put 65; put 10;
+println {^a}.a.inc!;
+println a.inc!;
+println a.inc!;
+
+put 66; put 10;
+println (b.inc!).i;
+println (b.inc!).i;
+println (b.inc!).i;
+
+# TODO: comments at eof don't parse
+println 42;

src/parser.rs

@@ -15,6 +15,9 @@ use logos::Logos;
 #[logos(skip r"[ \t\n\r\f]+")]
 #[logos(skip r"#[^\n]*?\n")]
 enum Token<'a> {
+    #[token("!")]
+    Bang,
+
     #[token(":")]
     Colon,
 
@@ -66,6 +69,7 @@ enum Token<'a> {
 impl fmt::Display for Token<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            Token::Bang => write!(f, "!"),
             Token::Colon => write!(f, ":"),
             Token::Period => write!(f, "."),
             Token::Comma => write!(f, ","),
@@ -234,14 +238,20 @@ where
 
         let e2 = access.or(e1);
 
-        let app = e2
+        let bang = e2.clone().foldl(just(Token::Bang).repeated(), |thunk, _| {
+            Ast::App(Box::new(thunk), Box::new(Ast::Block(vec![])))
+        });
+
+        let e3 = bang.or(e2);
+
+        let app = e3
             .clone()
-            .foldl(e2.clone().repeated(), |f, x| {
+            .foldl(e3.clone().repeated(), |f, x| {
                 Ast::App(Box::new(f), Box::new(x))
             })
             .labelled("function application");
 
-        let atom = app.or(e2);
+        let atom = app.or(e3);
 
         atom.pratt((
             infix(none(1), just(Token::BinOp("=")), |l, _, r, _| {

src/tests/parser.rs

@@ -215,3 +215,31 @@ if [wow = cool]() [
         ",
     );
 }
+
+#[test]
+fn bang() {
+    test(
+        "
+a := make_counter!;
+b := make_counter!;
+
+println {^a}.a.inc!;
+println a.inc!;
+println a.inc!;
+
+println b.inc!;
+println b.inc!;
+println b.inc!;
+",
+        "
+(set! a (make_counter ()));
+(set! b (make_counter ()));
+(println ({^a}.a.inc ()));
+(println (a.inc ()));
+(println (a.inc ()));
+(println (b.inc ()));
+(println (b.inc ()));
+(println (b.inc ()))
+",
+    );
+}