Contains definition of proto::domain<> class template and helpers for defining domains with a generator and a grammar for controlling operator overloading. Generator For use in defining domain tags to be used with proto::extends<>. A domain associates an expression type with a generator, and optionally a grammar. The Generator determines how new expressions in the domain are constructed. Typically, a generator wraps all new expressions in a wrapper that imparts domain-specific behaviors to expressions within its domain. (See proto::extends<>.) The Grammar determines whether a given expression is valid within the domain, and automatically disables any operator overloads which would cause an invalid expression to be created. By default, the Grammar parameter defaults to the wildcard, proto::_ , which makes all expressions valid within the domain. Example: template<typename Expr> struct MyExpr; struct MyGrammar : proto::or_< proto::terminal<_>, proto::plus<MyGrammar, MyGrammar> > {}; // Define MyDomain, in which all expressions are // wrapped in MyExpr<> and only expressions that // conform to MyGrammar are allowed. struct MyDomain : proto::domain<proto::generator<MyExpr>, MyGrammar> {}; // Use MyDomain to define MyExpr template<typename Expr> struct MyExpr : proto::extends<Expr, MyExpr<Expr>, MyDomain> { // ... }; Grammar proto::domain<> The domain expressions have by default, if proto::extends<> has not been used to associate a domain with an expression. A pseudo-domain for use in functions and metafunctions that require a domain parameter. It indicates that the domain of the parent node should be inferred from the domains of the child nodes. mpl::bool_< true-or-false > A metafunction that returns mpl::true_ if the type T is the type of a Proto domain; mpl::false_ otherwise. If T inherits from proto::domain<>, is_domain<T> is mpl::true_. A metafunction that returns the domain of a given type. If T is a Proto expression type, it returns that expression's associated domain. If not, it returns proto::default_domain. domain-of-T