Re: [Boost-users] [boost][lambda] additional placeholders

You would (if you already didn't) have to redefine CALL_TEMPLATE_ARGS, CALL_FORMAL_ARGS, and CALL_USE_ARGS macros too. Then it (might) work. The lambda code-base will change significantly with Phoenix-2, so I wouldn't invest too much time on this. In the future there will be support for at least 9 placeholders. Bets, Jaakko Järvi On Nov 17, 2005, at 3:34 PM, Noel Belcourt wrote:

HI,

I'm trying to extend the number of placeholders in boost lambda 1.33.0. There are three available by default and I need at least one more (_4) .

I've followed the pattern establish for _3 to define _4, modifying the following files along the way.

// lambda/core.hpp boost::lambda::placeholder3_type free3 = boost::lambda::placeholder3_type(); boost::lambda::placeholder4_type free4 = boost::lambda::placeholder4_type();

boost::lambda::placeholder3_type& _3 = free3; boost::lambda::placeholder4_type& _4 = free4;

// lambda/detail/lambda_functors.hpp template<> struct placeholder<FOURTH> { template<class SigArgs> struct sig { typedef typename detail::get_element_or_null_type<3, SigArgs>::type type; }; template RET call(CALL_FORMAL_ARGS) const { CALL_USE_ARGS; return c; } };

typedef const lambda_functor placeholder3_type; typedef const lambda_functor placeholder4_type;

// lambda/detail/arity_code.hpp enum { NONE = 0x00, // Notice we are using bits as flags here. FIRST = 0x01, SECOND = 0x02, THIRD = 0x04, FOURTH = 0x08, EXCEPTION = 0x10, RETHROW = 0x20};

So now _4 is defined but I get compilation errors from boost/function/function_template.hpp when I attempt to use _4. Is there some change necessary to either lambda placeholders or to boost function to get it to work correctly?

Thanks,

-- Noel Belcourt

// With the changes above, this code fails with the message below.

#include #include

using namespace boost; using namespace boost::lambda;

typedef function func_t;

template struct A { template <class R> A(void (R::*required)(T1, T2, T3, T4), R *r) : u(bind(required, r, _1, _2, _3, _4)) {} func_t u; };

struct B { void f(int, int, double, double); };

int main(int, char *[]) { B b; A a(&B::f, &b); return 0; }

This is the error message from CW 9.6 on Darwin

Error : call of non-function (point of instantiation: 'main(int, char **)') (instantiating: 'A::A<B>(void (B::*)(int, double, double), B *)') (instantiating: 'boost::function4::function4 `base constructor'>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>>(boost::lambda::lambda_functor>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>, int)') (instantiating: 'boost::function4::assign_to>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>>(boost::lambda::lambda_functor>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>)') (instantiating: 'boost::function4::assign_to>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>>(boost::lambda::lambda_functor>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>, boost::detail::function::function_obj_tag)') (instantiating: 'boost::detail::function::void_function_obj_invoker4>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>, void, int, int, double, double>::invoke(boost::detail::function::any_pointer, int, int, double, double)') function_template.hpp line 136 BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));

Error : call of non-function (instantiating: 'boost::detail::function::void_function_obj_invoker4>, boost::tuples::tuple>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, const boost::lambda::lambda_functor>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>>>, void, int, int, double, double>::invoke(boost::detail::function::any_pointer, int, int, double, double)') function_template.hpp line 136 BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));

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