feat: eq? operator

src/evaluator/env.rs

@@ -127,6 +127,20 @@ pub fn core_environment() -> Rc<Environment> {
                 Ok(Rc::new(Expression::HashMap(res)))
             }),
         ),
+        (
+            "eq?",
+            Expression::NativeFunc(|args| {
+                if args.len() != 2 {
+                    Err(Error::MismatchedArgCount(2, args.len()))?
+                }
+
+                if args[0] == args[1] {
+                    return Ok(TRUE.with(|inner| inner.clone()));
+                }
+
+                return Ok(FALSE.with(|inner| inner.clone()));
+            }),
+        ),
         (
             "not",
             Expression::NativeFunc(|args| {

src/evaluator/mod.rs

@@ -219,6 +219,9 @@ mod test {
     #[case("((fn* (a) a) 3)", "3")]
     #[case("((fn* (a) (+ a 2)) 1)", "3")]
     #[case("((fn* (a b) (+ a b)) 1 2)", "3")]
+    // Boolean operations
+    #[case("(eq? 1 1)", "true")]
+    #[case("(eq? 1 2)", "false")]
     #[case("(not false)", "true")]
     #[case("(not true)", "false")]
     #[case("(not nil)", "false")]