..

yielding · yielding · commit fe05af1f54c5 · 2023-09-25T08:19:49.000+09:00
diff --git a/cpp.fp/optional/optional.cpp b/cpp.fp/optional/optional.cpp
@@ -24,10 +24,10 @@ int main(int argc, char* argv[])
   vector_opt<string> v = { "1234", "15 foo", "bar", "42", "5000", " 5" };
 
   // NOTICE
-  // an operation which changes stored variable -> transform
-  // an operation which could itself fail -> and_then
+  // the functions inside and_then should an optional<T> as a result,
+  // the transform re-box the output of function into an optional<T> 
   auto filter = [](auto&& o) {
-    return o.and_then(to_int)   // flatmap from str to int
+    return o.and_then(to_int)      // flatmap from str to int
             .transform([](int n) { return n + 1; })
             .transform([](int n) { return to_string(n); })
             .or_else  ([]        { return optional("null"s); });
