Improve memory efficiency via plain ints for length

test/test_e2e.c

@@ -225,6 +225,36 @@ void test_complex(void) {
     TEST_ASSERT_OBJ_INT_V(response, 9);
 }
 
+void test_memory_perf_low(void) {
+    response = eval("(defun fib (n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))");
+
+    TEST_ASSERT_OBJ_SYMBOL_V(response, "fib");
+
+    response = eval("(fib 4)");
+
+    TEST_ASSERT_OBJ_INT_V(response, 3);
+}
+
+void test_memory_perf_medium(void) {
+    response = eval("(defun fib (n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))");
+
+    TEST_ASSERT_OBJ_SYMBOL_V(response, "fib");
+
+    response = eval("(fib 10)");
+
+    TEST_ASSERT_OBJ_INT_V(response, 55);
+}
+
+void test_memory_perf_high(void) {
+    response = eval("(defun fib (n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))");
+
+    TEST_ASSERT_OBJ_SYMBOL_V(response, "fib");
+
+    response = eval("(fib 8)");
+
+    TEST_ASSERT_OBJ_INT_V(response, 21);
+}
+
 int main(void) {
     UNITY_BEGIN();
 
@@ -254,6 +284,9 @@ int main(void) {
     RUN_TEST(test_nth_oob);
     RUN_TEST(test_eval_defun_gc);
     RUN_TEST(test_complex);
+    RUN_TEST(test_memory_perf_low);
+    RUN_TEST(test_memory_perf_medium);
+    RUN_TEST(test_memory_perf_high);
 
     return UNITY_END();
 }