Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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Struct by_value_generator

boost::proto::by_value_generator — A generator that replaces child nodes held by reference with ones held by value. Use with proto::compose_generators<> to forward that result to another generator.


// In header: <boost/proto/generate.hpp>

struct by_value_generator :  proto::callable {
  // member classes/structs/unions
  template<typename This, typename Expr> 
  struct result<This(Expr)> {
    // types
    typedef unspecified type;

  // public member functions
  template<typename Expr> unspecified operator()(Expr const &) const;


Generators are intended for use as the first template parameter to the proto::domain<> class template and control if and how expressions within that domain are to be customized. proto::by_value_generator ensures all child nodes are held by value. This generator is typically composed with a second generator for further processing, as proto::compose_generators<proto::by_value_generator, MyGenerator>.

by_value_generator public member functions

  1. template<typename Expr> unspecified operator()(Expr const & expr) const;



    A Proto expression.


    Equivalent to proto::deep_copy(expr)