The \pkgself~package exposes common and internal defintions. Ideally, this package will be included automatically by the compiler to remove repetitive, boilerplate imports. Importing this package isn't necessary if none of these definitions are needed.

\ref{_CMATCH_} is a magic constant that contains the result of a~classification match. This is used implicity by \ref{rate-each}.\footnote{The symbol is \Xi~because it looks like a sideways array.} \todo{Remove in favor of a local variable or generated classification; there is no need (anymore) for this to be magic.}

Primitives are defined internally; these definitions simply provide symbols to permit their use. \ref{empty} does not have much use outside of the compiler.

\ref{boolean} contains the boolean \ref{TRUE} and~\ref{FALSE} values, which map to~$1$ and~$0$ respectively. The \ref{maybe} type is the union of \ref{boolean} and \ref{NOTHING}, with a value of~$-1$;\footnote{ This is similar in spirit to the Haskell \tt{Maybe} type, or the OCaml \tt{Option} type. }this is commonly used to represent an unknown state or missing value.\footnote{ The \ref{nothing}~type is used for the sake of the union; it should not be used directly.} The constant \ref{UNKNOWN} is also defined as~$-1$ to serve as an alternative to the term~``nothing''.

$0$~is a~common value. Where a value is required (such as a~template argument), \ref{ZERO} may be used. TAME now supports a~constant-scalar syntax ({\tt #0}; \todo{reference this in documentation}), making this largely unnecessary. This is declared as a float to provide compatibility with all types of expressions. In the case where classifications are required, but a~static assumption about the applicability of the subject can be made, we have values that are always~true and always~false. The use of~\ref{never} may very well be a~code smell, but let us not rush to judgment.\footnote{\ref{never} has been added as an analog to~\ref{always}; its author has never had use for it. Oh, look, we just used ``never''.}

\ref{_todo_} formalizes TODO items and may optionally yield a value~\tt{@value@} for use within calculations.% \footnote{This is different than its previous behavior of always yielding a scalar~$0$.} All uses of the \ref{_todo_} template will produce a warning composed of its description~\tt{@desc@}. The \ref{_ignore_} template serves as a~block comment.\footnote{This is useful since XML does not support nested comments, which makes it difficult to comment out code that already has XML comments.} It may be useful for debugging, but is discouraged for use otherwise. The \ref{_ignore_/@desc@} param should be used to describe intent.

These templates represent calculations that used to be defined as XSLT templates before TAME's template system existed.

These templates alter the behavior of the TAME compiler or runtime. They will be removed at some point in the future.

The template \tt{_use-new-classification-system_} sets a compile-time flag that will cause all following sibling classifications to be compiled using the new classification system. Once the feature is enabled by default, this template will become a noop and will begin to emit a warning, before eventually being removed. It is possible to mix both old and new classifications within the same package, though such behavior may lead to confusion in certain cases. For more information on where the new and old system differ, see the \tt{core/test/core/class} specification.