Sexp parser

src/combinators.rs

@@ -107,6 +107,19 @@ where
     allow_trailing: bool,
 }
 
+impl<D, P, I, O, E> SeparatedBy<D, P, I, O, E>
+where
+    D: Parser<I, (), E>,
+    P: Parser<I, O, E>,
+    E: Default,
+{
+    pub fn allow_trailing(self, allow_trailing: bool) -> Self {
+        Self {
+            allow_trailing,
+            ..self
+        }
+    }
+}
 impl<D, P, I, O, E> Parser<I, Vec<O>, E> for SeparatedBy<D, P, I, O, E>
 where
     D: Parser<I, (), E>,

src/test/sexp.rs

@@ -53,7 +53,11 @@ fn parse_expr(input: &str) -> ParseResult<&str, Expr, ()> {
 
 fn parse_list(input: &str) -> ParseResult<&str, Expr, ()> {
     literal_char('(')
-        .ignore_then(repeated(parse_atom.map(Expr::Atom)).separated_by(whitespace.to(())))
+        .ignore_then(
+            repeated(parse_expr)
+                .separated_by(repeated(whitespace).at_least(1).to(()))
+                .allow_trailing(true),
+        )
         .then_ignore(literal_char(')'))
         .map(Expr::List)
         .parse(input)
@@ -71,4 +75,13 @@ fn test_parse_sexp() {
         ])
     );
     assert_eq!(output.1, "");
+
+    let complex_input = r#"
+(add (mul 28 9)
+    (if (eq a b) (jump #t) (hula 44))
+)"#
+    .trim();
+
+    let output = parse_expr(complex_input).unwrap();
+    assert_eq!(output.1, "");
 }