Re: compile time dependencies

From:
Barry <dhb2000@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 15 Nov 2007 21:15:39 +0800
Message-ID:
<fhhkvi$14n$1@news.cn99.com>
Zeppe wrote:

yurec wrote:

Hi

I can't compile

//#include <boost/function.hpp>

class boost::function;

UIStl * LoadStlFromAnotherProject(const CString & i_project_name,
boost::function<bool (MSAXReader &,UIObject *)> i_func_compare);

1. Parameter and return types need only to be forward-declared.
(Herb Sutter , Exceptional C++: 47 Engineering Puzzles, Programming
Problems, and Solutions, Item 26)

Can anybody tell me correct syntax?


You have to include the header, because you are instantiating a template
class.


It's not necessary

<std>
14.7.3/10
A template-id that names a class template explicit specialization that
has been declared but not defined can be used exactly like the names of
other incompletely-defined classes (3.9). [Example:
    template<class T> class X; // X is a class template
    template<> class X<int>;
    X<int>* p; // OK: pointer to declared class X<int>
    X<int> x; // error: object of incomplete class X<int>
end example]
</std>

here is how what the op want,
anyway, I don't suggest this :-)

<code>
namespace boost {
     template <class, class>
     class function;
}

#include <boost/function.hpp>

void invoke(boost::function<int(int)>& f) {
     f(10);
}

#include <iostream>

int f(int i) { std::cout << i << std::endl; return i; }

int main() {
     boost::function<int(int)> fobj(f);
     invoke(fobj);
}
</code>

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