Re: [Boost-users] [function] How do you bind two boost::function objects together?

From: Douglas Gregor (doug.gregor_at_[hidden])
Date: 2006-10-01 09:43:58

On Sep 30, 2006, at 1:01 PM, Jason House wrote:

> I'm trying to convert the input argument to a function object using a
> small helper function object.  The code below looks relatively simple,
> but it doesn't seem to compile.  Any ideas what could be wrong?
>
> template<typename inputType, typename outputType>
> boost::function<outputType (int)>
> convert(boost::function<outputType (inputType)> &object_to_convert){
>    boost::function<intputType (int)> input_converter(...);
>
>    // The following fails to compile
>    boost::function<outputType (int)> converted_function
>      (boost::lambda::bind(object_to_convert, input_converter));

The bind expression is going to result in a function object that  
calls object_to_convert(input_converter). What you really want is a  
function object that takes one parameter ("arg1") and call  
object_to_object with the result of input_converter(arg1). To do so,  
you will need a nested bind expression that will look something like  
this:

   boost::function<outputType (int)> converted_function
    (boost::lambda::bind(object_to_convert, boost::lambda::bind 
(input_converter, arg1)));

        Cheers,
        Doug