Text placement type in TextSymbolizer with C++

[Petra Millarova]

Hello, 

I would like to try out the text placements options that are mentioned on the wiki here under "Placements". I am using Mapnik 3.1.0, however I do not know how to initialize other placements than the ones of type  text_placements_dummy, which I do like this and it works fine:

text_placements_ptr plc = std::make_shared<text_placements_dummy>();

However this doesn't work when I try to initialize the type simple or list, so how do I use those? Are there any arguments I should pass on upon creation? The documentation of Mapnik 3 in C++ is close to non-existent on the wiki and I couldn't find any other useful information 

Thank you for your time, 

Petra M.