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Struct template impl

boost::proto::when<Grammar, R(A...)>::impl

Synopsis

// In header: <boost/proto/transform/when.hpp>


template<typename Expr, typename State, typename Data> 
struct impl :  proto::transform_impl< Expr, State, Data > {
  // types
  typedef proto::call<R(A...)>                                       call_;        // For exposition only
  typedef proto::make<R(A...)>                                       make_;        // For exposition only
  typedef typename mpl::if_<proto::is_callable<R>,call_,make_>::type which;        // For exposition only
  typedef typename boost::result_of<which(Expr, State, Data)>::type  result_type;

  // public member functions
  result_type operator()(typename impl::expr_param, 
                         typename impl::state_param, 
                         typename impl::data_param) const;
};

Description

impl public member functions

  1. result_type operator()(typename impl::expr_param expr, 
                           typename impl::state_param state, 
                           typename impl::data_param data) const;

    Evaluate R(A...) as a transform either with proto::call<> or with proto::make<> depending on whether proto::is_callable<R>::value is true or false.

    Parameters:

    data

    An arbitrary data

    expr

    The current expression

    state

    The current state

    Requires:

    proto::matches<Expr, Grammar>::value is true.

    Returns:

    which()(expr, state, data)


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