[Boost-users] Boost.Parameter python and lazy evaluation of default arguments

Subject: [Boost-users] Boost.Parameter python and lazy evaluation of default arguments
From: Philipp Büttgenbach (Philipp.Buettgenbach_at_[hidden])
Date: 2017-06-05 13:19:11

Hello all,

I have a question concerning the Boost.Parameter library and the python
binding provided by this library.

When I try to compile the attached code with clang I get:

-------------------------------
/tmp$ clang -I/usr/include/python2.7/ -std=c++14 -c python_test.cpp 
In file included from python_test.cpp:7:
In file included from /usr/include/boost/parameter/preprocessor.hpp:8:
In file included from /usr/include/boost/parameter/parameters.hpp:40:
/usr/include/boost/parameter/aux_/arg_list.hpp:361:16: error: no viable
      conversion from 'boost::parameter::aux::maybe<std::basic_string<char> >'
      to 'const std::basic_string<char>'
        return arg.value;
               ^~~~~~~~~
-------------------------------

If I just compile main or use standard default arguments everything
compiles fine.

Can anybody explain to me what's wrong with using lazy default argument
evaluation when exporting to python?

Thanks a lot,

Philipp