In boost 1.56 the optional library is no longer happy with the implicit
conversion from boost::optional<std::string> to bool, so we get the following
errors:
valijson/include/valijson/schema.hpp:177:16: error: no viable conversion from 'const boost::optional<std::string>' to 'bool'
return id;
^~
valijson/include/valijson/schema.hpp:188:16: error: no viable conversion from 'const boost::optional<std::string>' to 'bool'
return title;
^~~~~
2 errors generated.
Here we explicitly test against boost::none instead.
This commit contains the third major design of a C++ library for JSON Schema validation.
It is definitely not what I would consider production-ready, but I do think that the overall design of the library is robust.
