[Boost-users] [lambda] "Invalid use of void expression"

From: David A. Greene (greened_at_[hidden])
Date: 2006-01-24 09:18:54

I'm having some trouble with BLL and Boost.Function in this simple
testcase:

#include <boost/lambda/bind.hpp>
#include <boost/function.hpp>

#include <iostream>

class Test {
public:
   void foo(int a) { std::cout << "a is " << a << std::endl; };
};

template<typename Function>
class Caller {
private:
   Function func;

public:
   Caller(Function f) : func(f) {};

   void bar(void) { func(); };
};

int main(void)
{
   Test tester;
   int value = 10;

   Caller<boost::function<void (void)> > 
printer(boost::lambda::bind(boost::lambda::bind(&Test::foo, tester, 
boost::lambda::_1), value));

   printer.bar();

   return(0);
}

The g++ 4.0.3 compiler complains (full trace below):

/usr/include/boost/lambda/detail/lambda_functor_base.hpp:408: error: 
invalid use of void expression

Is it not legal to bind a lambda-bound function?

                              -Dave

----------------------
/usr/include/boost/lambda/detail/lambda_functor_base.hpp: In member 
function 'RET 
boost::lambda::lambda_functor_base<boost::lambda::action<2, Act>, 
Args>::call(A&, B&, C&, Env&) const [with RET = 
boost::tuples::null_type, A = const boost::tuples::null_type, B = const 
boost::tuples::null_type, C = const boost::tuples::null_type, Env = 
const boost::tuples::null_type, Act = boost::lambda::function_action<2, 
boost::lambda::detail::unspecified>, Args = boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type>]':
/usr/include/boost/lambda/detail/lambda_functors.hpp:140:   instantiated 
from 'typename T::sig<boost::tuples::null_type>::type 
boost::lambda::lambda_functor<Base>::operator()() const [with T = 
boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> >]'
/usr/include/boost/function/function_template.hpp:136:   instantiated 
from 'static void 
boost::detail::function::void_function_obj_invoker0<FunctionObj, 
R>::invoke(boost::detail::function::any_pointer) [with FunctionObj = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void]'
/usr/include/boost/function/function_template.hpp:479:   instantiated 
from 'void boost::function0<R, Allocator>::assign_to(FunctionObj, 
boost::detail::function::function_obj_tag) [with FunctionObj = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:430:   instantiated 
from 'void boost::function0<R, Allocator>::assign_to(Functor) [with 
Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:294:   instantiated 
from 'boost::function0<R, Allocator>::function0(Functor, typename 
boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, 
int>::type) [with Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:637:   instantiated 
from 'boost::function<R ()(), Allocator>::function(Functor, typename 
boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, 
int>::type) [with Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
lambda3.cc:27:   instantiated from here
/usr/include/boost/lambda/detail/lambda_functor_base.hpp:408: error: 
invalid use of void expression
/usr/include/boost/lambda/detail/actions.hpp: In static member function 
'static RET boost::lambda::function_action<3, T>::apply(A1&, A2&, A3&) 
[with RET = void, A1 = void (Test::* const)(int), A2 = const Test, A3 = 
const boost::tuples::null_type, T = boost::lambda::detail::unspecified]':
/usr/include/boost/lambda/detail/lambda_functor_base.hpp:425: 
instantiated from 'RET 
boost::lambda::lambda_functor_base<boost::lambda::action<3, Act>, 
Args>::call(A&, B&, C&, Env&) const [with RET = void, A = const 
boost::tuples::null_type, B = const boost::tuples::null_type, C = const 
boost::tuples::null_type, Env = const boost::tuples::null_type, Act = 
boost::lambda::function_action<3, boost::lambda::detail::unspecified>, 
Args = boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type>]'
/usr/include/boost/lambda/detail/select_functions.hpp:61:   instantiated 
from 'static RET boost::lambda::detail::r_select<RET>::go(const 
boost::lambda::lambda_functor<Arg>&, A&, B&, C&, Env&) [with Arg = 
boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> >, A = const boost::tuples::null_type, B = 
const boost::tuples::null_type, C = const boost::tuples::null_type, Env 
= const boost::tuples::null_type, RET = void]'
/usr/include/boost/lambda/detail/lambda_functor_base.hpp:408: 
instantiated from 'RET 
boost::lambda::lambda_functor_base<boost::lambda::action<2, Act>, 
Args>::call(A&, B&, C&, Env&) const [with RET = 
boost::tuples::null_type, A = const boost::tuples::null_type, B = const 
boost::tuples::null_type, C = const boost::tuples::null_type, Env = 
const boost::tuples::null_type, Act = boost::lambda::function_action<2, 
boost::lambda::detail::unspecified>, Args = boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type>]'
/usr/include/boost/lambda/detail/lambda_functors.hpp:140:   instantiated 
from 'typename T::sig<boost::tuples::null_type>::type 
boost::lambda::lambda_functor<Base>::operator()() const [with T = 
boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> >]'
/usr/include/boost/function/function_template.hpp:136:   instantiated 
from 'static void 
boost::detail::function::void_function_obj_invoker0<FunctionObj, 
R>::invoke(boost::detail::function::any_pointer) [with FunctionObj = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void]'
/usr/include/boost/function/function_template.hpp:479:   instantiated 
from 'void boost::function0<R, Allocator>::assign_to(FunctionObj, 
boost::detail::function::function_obj_tag) [with FunctionObj = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:430:   instantiated 
from 'void boost::function0<R, Allocator>::assign_to(Functor) [with 
Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:294:   instantiated 
from 'boost::function0<R, Allocator>::function0(Functor, typename 
boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, 
int>::type) [with Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
/usr/include/boost/function/function_template.hpp:637:   instantiated 
from 'boost::function<R ()(), Allocator>::function(Functor, typename 
boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, 
int>::type) [with Functor = 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, 
boost::lambda::function_action<2, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<const 
boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<3, 
boost::lambda::function_action<3, boost::lambda::detail::unspecified> >, 
boost::tuples::tuple<void (Test::* const)(int), const Test, const 
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, const int, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type, boost::tuples::null_type, 
boost::tuples::null_type> > >, R = void, Allocator = std::allocator<void>]'
lambda3.cc:27:   instantiated from here
/usr/include/boost/lambda/detail/actions.hpp:96: error: no matching 
function for call to 'boost::lambda::function_adaptor<void 
(Test::*)(int)>::apply(void (Test::* const&)(int), const Test&, const 
boost::tuples::null_type&)'
/usr/include/boost/lambda/detail/function_adaptors.hpp:245: note: 
candidates are: static Result boost::lambda::function_adaptor<Result 
(Object::*)(Arg1)>::apply(Result (Object::*)(Arg1), Object*, A1&) [with 
RET = void, A1 = const boost::tuples::null_type, Object = Test, Arg1 = 
int, Result = void]
/usr/include/boost/lambda/detail/function_adaptors.hpp:249: note: 
           static Result boost::lambda::function_adaptor<Result 
(Object::*)(Arg1)>::apply(Result (Object::*)(Arg1), Object&, A1&) [with 
RET = void, A1 = const boost::tuples::null_type, Object = Test, Arg1 = 
int, Result = void]
/usr/include/boost/lambda/detail/actions.hpp:96: error: return-statement 
with a value, in function returning 'void'