Re: [Boost-Users] return type of bind object

On Friday 14 March 2003 09:45 pm, Faheem Mitha wrote:

Dear People,

I have defined a function as follows.

double accept_prob_fn(const double x, const double be, const double theta, const double a, const double b);

Now, I define the temporary function object

bind(accept_prob_fn, _1, be, theta, a, b);

So this function object would return the first argument, x. However, I want to save this function object to a function object called foo, say.

So I want to do something like

Type foo = bind(accept_prob_fn, _1, be, theta, a, b);

However, the problem I have is that I'm not sure what type foo should be. I forced an error with my compiler (to try to see what it thought the type of the rhs should be) by using Type as double, but all I got was

brent.cc:9: cannot convert `boost::_bi::bind_t, boost::_bi::value<double>, boost::_bi::value<double>, boost::_bi::value<double>, boost::_bi::value<double> > >' to `double' in initialization

Eww.

I've tried looking at the documentation, but I find it pretty much incomprehensible. Could someone

a) Tell me what "Type" should be.

The type is "unspecified", may vary from compiler to compiler, and is hideous on every compiler. For these reasons, it's intentional that you can't name the type directly (see http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1438.htm, section IIIB). However, you can include and make the Type: boost::function (or, if your compiler isn't up to par, boost::function1). See the Boost.Function documentation for more information about the Function library. Doug