These modifications ensure enum.h can be used in a wider
selection of end user projects without triggering warnings.
GCC 4.9.2 was used with the following warning flags set:
-Wall -Wextra -Wshadow -Weffc++ -Wno-unused-parameter
-Wno-unused-local-typedefs -Wno-long-long -Wstrict-aliasing
-Werror -pedantic -std=c++1y -Wformat=2 -Wmissing-include-dirs
-Wsync-nand -Wuninitialized -Wconditionally-supported -Wconversion
-Wuseless-cast -Wzero-as-null-pointer-constant
This commit includes the modifications required to enable successful
use of enum.h via both the "test" and "example" directories.
These return values of an optional type better_enums::optional<T>. This type is
defined in the spirit of boost::optional<T> and std::optional<T>, but is easy to
manipulate at compile time. Two additional macros BETTER_ENUMS_USE_OPTIONAL and
BETTER_ENUMS_EXTRA_INCLUDE are honored, whose intent is for the user to be able
to inject an alternative option type. However, there are currently no viable
alternatives. boost::optional<T> does not play well with constexpr, and I failed
to make the code compile with std::optional<T>. I did not try very hard. I
intend to support std::optional<T> in the future. Perhaps it will be the
default, when available.
