Evaluate both side of application

2 files changed, 18 insertions, 4 deletions

diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index 0080f63..b05bd22 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -17,7 +17,7 @@ pub fn run(arg: &str) -> String {
 
 fn interpret(arg: &Value) -> Value {
     match arg {
-        Value::App(l, r) => apply(&interpret(l), r),
+        Value::App(l, r) => apply(&interpret(l), &interpret(r)),
         other => other.clone(),
     }
 }
@@ -87,4 +87,11 @@ mod lambda_test {
         let value = parse("(((lam x (lam x x)) 13) 12)");
         assert_eq!(Value::Num(12), interpret(&value));
     }
+
+    #[test]
+    fn interpretation_applies_to_both_sides_of_application() {
+        let value = parse("((lam x x) ((lam x x) 12))");
+        assert_eq!(Value::Num(12), interpret(&value));
+    }
+
 }
diff --git a/rust/src/parser.rs b/rust/src/parser.rs
index c85a425..9dc0bb8 100644
--- a/rust/src/parser.rs
+++ b/rust/src/parser.rs
@@ -250,12 +250,19 @@ mod tests {
         type Strategy = BoxedStrategy<Self>;
 
         fn arbitrary_with(_args: ()) -> Self::Strategy {
-            prop_oneof![
+            let identifier = "\\pL(\\pL|\\pN)*";
+            let leaf = prop_oneof![
                 any::<i32>().prop_map(Num),
                 any::<bool>().prop_map(Bool),
                 // see https://unicode.org/reports/tr18/#General_Category_Property for one letter unicode categories
-                "\\pL(\\pL|\\pN)*".prop_map(Sym),
-            ]
+                identifier.prop_map(Sym),
+            ];
+            leaf.prop_recursive(4, 128, 5, move |inner| {
+                prop_oneof![
+                    (inner.clone(), inner.clone()).prop_map(|(l, r)| App(Box::new(l), Box::new(r))),
+                    (identifier, inner).prop_map(|(var, body)| Lam(var, Box::new(body))),
+                ]
+            })
             .boxed()
         }
     }