Re: [Boost-users] [phoenix] adding const to member_variable bind

Subject: Re: [Boost-users] [phoenix] adding const to member_variable bind
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-11-11 22:21:48

AMDG

Joel de Guzman wrote:
>> There is no way for result to distinguish between these cases,
>> even though they are different.
>
> Out of curiosity, how does Boost.Bind and Lambda.Bind behave in this
> regard?

It looks like:
a) bind always constifies the return type of a pointer to a data member.
b) lambda does not strip references in its return type deduction.

#include <boost/spirit/home/phoenix/bind.hpp>
#include <boost/spirit/home/phoenix/core.hpp>

#include <boost/bind.hpp>
#include <boost/ref.hpp>
#include <boost/lambda/bind.hpp>

struct x {
    int m;
};

void boost_bind() {
    using namespace boost;
    x x_ = {0};
    bind(&x::m, x_)();
    bind(&x::m, ref(x_))() = 1; // does not compile--returns const int&
    bind(&x::m, cref(x_))();
}

void boost_lambda() {
    namespace lambda = boost::lambda;
    x x_ = {0};
    lambda::bind(&x::m, x_)();
    lambda::bind(&x::m, lambda::var(x_))() = 1;
    lambda::bind(&x::m, lambda::var(static_cast<const x&>(x_)))();
}

void boost_phoenix() {
    namespace phoenix = boost::phoenix;
    x x_ = {0};
    phoenix::bind(&x::m, phoenix::val(x_))(); // does not compile
    phoenix::bind(&x::m, phoenix::ref(x_))() = 1;
    phoenix::bind(&x::m, phoenix::cref(x_))(); // does not compile
}

In Christ,
Steven Watanabe