typeval

An experiment in constexpr parameters.

A note on macro naming: For options, use TV_OPTION_ON and TV_OPTION_OFF (i.e., for the KEYWORD option, you'd define TV_OPTION_OFF_KEYWORD if you didn't want the typeval keyword to be defined). If one defines both, the library will error at you. For standard defaults, use TV_STD_CPPXY; the default option is CPP14. Internal macros are denoted by TV_INTERNAL - do not touch these.

Options:

• VARIABLE_TEMPLATES -- Whether to define variable templates (_v templates)

• DECLTYPE_AUTO -- Whether to use decltype(auto), or -> decltype(...). With the latter, you can't use typeval with lambdas, but it's legal under C++11

• KEYWORD -- Whether to define typeval (otherwise, use TV_MAKE_TYPEVAL)

• CONSTEXPR_LAMBDA -- Whether to make the lambdas constexpr. This is the only way one would be able to use make_typeval in a constant expression.

Standard defaults:

• CPP11:
  • VARIABLE_TEMPLATES - off
  • CONSTEXPR_LAMBDA - off
  • DECLTYPE_AUTO - off
• CPP14 (default):
  • VARIABLE_TEMPLATES - on
  • CONSTEXPR_LAMBDA - off
  • DECLTYPE_AUTO - on
• CPP17
  • VARIABLE_TEMPLATES - on
  • CONSTEXPR_LAMBDA - on
  • DECLTYPE_AUTO - on

KEYWORD is on by default in all standards