- Working on expressions, trying to reduce template instantiation.
- Continuing experimentation with expressions.
- Fixed a bug with is_variable not checking detail::return_type.
- Added an is_trivial expression evaluation. (Trivial expressions have 1 or fewer arguments)
- Added comments to all important structures.
- Changes `is_const` and `is_nonconst` to `is_functionally_const` and `is_functionally_nonconst` for more clarity.
- Changed `is_function` to `is_functional` to stick with the naming convention.
- The definition of `is_functionally_const` changed. It no longer supports const member variables, as they are not functional.
- A couple more tests, and slight fixes to the current test results to reflect the changed information.
- Fixed a bug when requesting the  the expressions of an expression.
- Removed sample code. (Will put in different file.)
- Commit sample expressions code.
- Added is_variadic/is_nonvariadic to expressions.