Re: [Boost-users] Why does gcc require explicit template arguments with my boost::bind

Subject: Re: [Boost-users] Why does gcc require explicit template arguments with my boost::bind
From: Thomas Heller (thom.heller_at_[hidden])
Date: 2012-12-06 08:02:43

On 12/06/2012 06:34 AM, Chris Stankevitz wrote:
> Hello,
>
> Below I implement a function "Chain" that takes two functions and
> executes them both.
>
> The first approach succeeds: direct function call.
>
> The second approach succeeds: call via bind with explicit template arguments
>
> The third and fourth approaches fail: call via bind without explicit
> template arguments (with/without boost::protect)
>
> Question: Why do I have to use explicit template arguments when using
> bind with Chain?
Chain is a template function. Its address isn't known until it gets 
instantiated. In order to bind a function, bind needs to know the 
address (aka which function to bind to). This means, that you have to 
specify the complete type.
>
> Thank you,
>
> Chris
>
> ===
>
> #include<boost/bind.hpp>
> #include<boost/function.hpp>
>
> template<typename TAFunc1, typename TAFunc2>
> void Chain(const TAFunc1&  Func1, TAFunc2&  Func2)
> {
>     Func1();
>     Func2();
> }
>
> void f()
> {
> }
>
> void foo()
> {
>    boost::function<void()>  x = boost::bind(f);
>
>    boost::function<void()>  y = boost::bind(f);
>
>    Chain(x, y);
>
>    boost::bind(Chain<boost::function<void()>, boost::function<void()>  >, x, y)();
>
>    boost::bind(Chain, x, y)();
>
>    boost::bind(Chain, boost::protect(x), boost::protect(y))();
> }
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