<\body> The primitives in this section are merely for internal use by only. They are documented for the sake of completeness, but you should only use them if you really know what you are doing. <\explain|> This primitive is mainly used for default uninialized value of environment variables; the main advantage of this tag is to be distinct from the empty string. <\explain|> This primitive should never appear in documents. It is provided as aid in tracking down invalid constructs. It is produced at evaluation time by any kind of primitive which is given improper operands. <\explain> >|binding-n> <|explain> The tag is used to represent hashtables with bindings until . Each binding is of the form , with a and an associated . <\explain> >|key-n|val-n> <|explain> This tag is included for future compatability with XML. It is used for encoding XML-style attributes by trees. For instance, the fragment <\quote-env> \blah color="blue" emotion="verbose"\ \ \ Some XML stuff \/blah\ > would typically be represented as <\tm-fragment> |Some XML stuff>> <\explain> <|explain> Associate a special meaning to some . Currently, no real use has been made of these tags. <\explain> <|explain> Used to represent temporarily saved values on a stack. <\explain> <|explain> This primitive is only intended for internal use by the , and primitives. <\explain> <|explain> This internal primitive is used for rewriting an inactive tree into a new tree whose rendering corresponds to the rendering of the inactive tree. <\explain> <|explain> Yet to be implemented primitives for starting a new double page. <\explain> <|explain> The identity macro is built-in into . It should not really be considered as a primitive, but it is not part of any style file either. In addition to these primitives for internal use only, there are also quite a few obsolete primitives, which are no longer being used by , but whose names should be avoided when creating your own macros. The full list of obsolete primitives is: , , , , , , , , , , , , , , , , , , .