cxx-prettyprint | A header-only library for C that allows automagic

I'm trying to get some data-driven test cases running with BOOST_DATA_TEST_CASE and figured out the basics o far.

However, I noticed that the type that is used as sample input MUST be printable:

This will work:

I'm writing approval tests using the excellent ApprovalTests.cpp library. This library automates generation of "snapshots" of results from a function. Snapshots are generated serializing results of type T to a file using the ostream& operator<< (T val).

This operator has always been the C++ convention for formatting some value to a textual representation. While primitive types support this operator and you can write your own implementation for custom types, there isn't a standard implementation for STL containers like std::vector.

You can implement your own, even using other libraries like fmt or pprint. Here are some example with similar outputs. I use the generic type STREAM as parameter instead of the concrete type ostream as recommended by ApprovalTests.cpp but the idea doesn't change.

pretty print container of arbitrary type

The following code of few lines provides same output as prettyprint.hpp in question, but the output stream is limited to std::cout.

How to rewrite those code using boost::hof to provide print(std::ostream&, ...) like interface?