ptr_func and unary_function need to be removed for compatibility with c++ > 14

[fbergmann]

The conda build logs marked ptr_func as deprecated. So we should add detection of c++17, and if it is detected use a lambda instead. Here the warning:

2020-08-10T08:25:14.6208170Z   /tmp/pip-req-build-q_svt3q_/libsbml_source/src/sbml/packages/comp/util/SBMLUri.cpp:157:5: warning: 'ptr_fun<int, int>' is deprecated [-Wdeprecated-declarations]
2020-08-10T08:25:14.6210590Z       ptr_fun<int,int>(tolower)); // scheme is icase
2020-08-10T08:25:14.6211440Z       ^
2020-08-10T08:25:14.6212860Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/functional:1107:1: note: 'ptr_fun<int, int>' has been explicitly marked deprecated here
2020-08-10T08:25:14.6213640Z   _LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
2020-08-10T08:25:14.6214530Z   ^
2020-08-10T08:25:14.6215740Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/__config:972:39: note: expanded from macro '_LIBCPP_DEPRECATED_IN_CXX11'
2020-08-10T08:25:14.6216480Z   #  define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
2020-08-10T08:25:14.6216890Z                                         ^
2020-08-10T08:25:14.6218130Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/__config:961:48: note: expanded from macro '_LIBCPP_DEPRECATED'
2020-08-10T08:25:14.6218880Z   #    define _LIBCPP_DEPRECATED __attribute__ ((deprecated))
2020-08-10T08:25:14.6219280Z                                                  ^
2020-08-10T08:25:14.6258400Z   /tmp/pip-req-build-q_svt3q_/libsbml_source/src/sbml/packages/comp/util/SBMLUri.cpp:198:6: warning: 'ptr_fun<int, int>' is deprecated [-Wdeprecated-declarations]
2020-08-10T08:25:14.6259640Z        ptr_fun<int,int>(tolower)); // host is icase
2020-08-10T08:25:14.6260290Z        ^
2020-08-10T08:25:14.6262420Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/functional:1107:1: note: 'ptr_fun<int, int>' has been explicitly marked deprecated here
2020-08-10T08:25:14.6263460Z   _LIBCPP_DEPRECATED_IN_CXX11 inline _LIBCPP_INLINE_VISIBILITY
2020-08-10T08:25:14.6264090Z   ^
2020-08-10T08:25:14.6266030Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/__config:972:39: note: expanded from macro '_LIBCPP_DEPRECATED_IN_CXX11'
2020-08-10T08:25:14.6266940Z   #  define _LIBCPP_DEPRECATED_IN_CXX11 _LIBCPP_DEPRECATED
2020-08-10T08:25:14.6267440Z                                         ^
2020-08-10T08:25:14.6268660Z   /usr/local/miniconda/conda-bld/python-libsbml_1597047524118/_build_env/bin/../include/c++/v1/__config:961:48: note: expanded from macro '_LIBCPP_DEPRECATED'
2020-08-10T08:25:14.6269410Z   #    define _LIBCPP_DEPRECATED __attribute__ ((deprecated))
2020-08-10T08:25:14.6269890Z                                                  ^
2020-08-10T08:25:15.1972140Z   2 warnings generated.

[otronarp]

There is also a lot of use of std::unary_function and that one was also removed in c++17.

[otronarp]

There is also a lot of use of std::unary_function and that one was also removed in c++17.

The use of std::unary_function is actually worse since that's in the header files so it spill over on client code. Meaning that if you use libsbml you are stuck at using c++14.

[fbergmann]

agreed, i'm doing some testing right now on what compilers it is actually needed, but it seems to compile fine even on older versions of g++ / msvc without it