update to show a calculation

main.c

@@ -4,6 +4,7 @@ int main(int argc, char *argv[])
 {
     ruby_init();
     ruby_init_loadpath();
-    rb_eval_string("puts 'Hello, C world from Ruby'");
+    VALUE v = rb_eval_string("3 + 8");
+    printf("v: %d\n", FIX2INT(v));
     return 0;
 }