Re: [Boost-users] return type of boost::bind

From: Cheenu Srinivasan (cheenu_srinivasan_at_[hidden])
Date: 2004-02-01 14:09:51

Duane Murphy wrote:
> The return type of boost::bind is fairly indeterminate. In order to call
> a bound function at a later time, look at boost::function. It does a nice
> job of holding on to a function that uses boost::bind.

I looked at "Using bind with Boost.Function" in the boost::function docs.
Mimicing that, for my example, I tried:

  boost::function<double (int)> bound_func = boost::bind(f, _1, 1.234);
  int i = 99;
  cout << bound_func(i) << endl;

but it throws a bad_function_call exception when bound_func(i) is invoked.
How do I use boost::function for this situation?

Thanks.
Cheenu

I wrote:
> >I wish to store the return value of boost::bind in an intermediate object
> >to invoke it at a later time.  I only ever see examples which combine
> >the call to boost:bind with the immediate invocation on the returned
> >object such as:
> >
> >    #include <boost/bind.hpp>
> >    using namespace boost;
> >    #include <iostream>
> >    using namespace std;
> >
> >    double f(int i, double d) {
> >      cout << "int = " << i << endl;
> >      return d;
> >    }
> >
> >    main() {
> >      int i = 99;
> >      cout << bind(f, _1, 1.234)(i) << endl;
> >    }
> >
> >Instead I'd like to postpone the call to the returned object.  What's the 
> >type of obj?
> >
> >  main() {
> >    int i = 99;
> >    WHAT_IS_MY_TYPE obj = bind(f, _1, 1.234);
> >    ...
> >    cout << obj(i) << endl;
> >  }