boost::proto::exprns_::is_proto_expr Struct Reference

Empty type to be used as a dummy template parameter of POD expression wrappers. More...

#include <extends.hpp>

Detailed Description

Empty type to be used as a dummy template parameter of POD expression wrappers.

It allows argument-dependent lookup to find Proto's operator overloads.

proto::is_proto_expr allows argument-dependent lookup to find Proto's operator overloads. For example:

template<typename T, typename Dummy = proto::is_proto_expr>
struct my_terminal
{
    BOOST_PROTO_BASIC_EXTENDS(
        typename proto::terminal<T>::type
      , my_terminal<T>
      , default_domain
    )
};

// ...
my_terminal<int> _1, _2;
_1 + _2; // OK, uses proto::operator+

Without the second Dummy template parameter, Proto's operator overloads would not be considered by name lookup.

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The documentation for this struct was generated from the following file:

• boost_1_57_0/boost/proto/extends.hpp