From: Korcan Hussein Sent: 20 February 2008 15:06 To: boost@lists.boost.org Subject: [boost] [bind] recursively binding higher-order functional objects fails to compile.

Sorry about the poor title, it is difficult for me to explain the problem without code so here is a really simple example of what i'm trying to achieve but fails to compile with Boost.Bind:

#include <boost/bind.hpp>

struct FunFn {

typedef void result_type; template < typename Fun > void operator()(Fun fn) const { fn(); }

} const Fn;

void g() { std::cout << "hello\n"; }

int main() { using namespace boost;

bind(Fn, bind(Fn, bind(Fn, bind(Fn, ... bind(Fn, g))();

Clearly: bind(Fn,g)(); works. What about: bind(Fn, bind(Fn, g))(); If that works, how many binds can you add before it stops working?

}

I get type deduction errors,

You may have run into a compiler limit. What compiler are you using?

however i have found workaround using Boost.Function for the time being:

#include <boost/function.hpp>

... boost::function< void () > fnN = bind(Fn, g), fnN-1 = bind(Fn, fnN), ..., fn1 = bind(Fn, fn2), fn = bind(Fn, fn1);

bind(Fn, fn)();

-- Martin Bonner Senior Software Engineer/Team Leader PI SHURLOK LTD Telephone: +44 1223 441434 / 203894 (direct) Fax: +44 1223 203999 Email: martin.bonner@pi-shurlok.com www.pi-shurlok.com disclaimer

AMDG Korcan Hussein wrote:

Sorry about the poor title, it is difficult for me to explain the problem without code so here is a really simple example of what i'm trying to achieve but fails to compile with Boost.Bind:

#include <boost/bind.hpp>

struct FunFn {

typedef void result_type; template < typename Fun > void operator()(Fun fn) const { fn(); }

} const Fn;

void g() { std::cout << "hello\n"; }

int main() { using namespace boost;

bind(Fn, bind(Fn, bind(Fn, bind(Fn, ... bind(Fn, g))();

}

This creates a function object that executes: Fn(Fn(Fn(g()))) Since the inner functions return void, of course it fails.

I get type deduction errors, however i have found workaround using Boost.Function for the time being:

#include <boost/function.hpp>

... boost::function< void () > fnN = bind(Fn, g), fnN-1 = bind(Fn, fnN), ..., fn1 = bind(Fn, fn2), fn = bind(Fn, fn1);

bind(Fn, fn)();

In Christ, Steven Watanabe