Unable to dump to stringstream

[tjespe]

• What is the issue you have?
  Tried to dump to an ostringstream as specified was possible in the documentation, but cannot compile because the compiler can't find a match for the overloaded operator.

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?

json res = json::object();
std::ostringstream to;
to << res;

• What is the expected behavior?
  It should compile and dump to stream correctly.

• And what is the actual behavior instead?
  Compilation error.

error: no match for ‘operator<<’ (operand types are ‘std::ostringstream’ {aka ‘std::__cxx11::basic_ostringstream<char>’} and ‘json’ {aka ‘nlohmann::basic_json<>’})
  136 |     to << res;
      |     ~~ ^~ ~~~
      |     |     |
      |     |     json {aka nlohmann::basic_json<>}
      |     std::ostringstream {aka std::__cxx11::basic_ostringstream<char>}

• Which compiler and operating system are you using? Is it a supported compiler?

gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0

• Did you use a released version of the library or the version from the develop branch?

I am using release v3.7.3 from https://github.com/ArthurSonzogni/nlohmann_json_cmake_fetchcontent

• If you experience a compilation error: can you compile and run the unit tests?
  All unit tests passed

[tjespe]

Turns out I had forgotten to include the sstream header