[Boost-users] lambda problem

, 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> > >, const int, boost::lambda::lambda_functor >, 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:148: instantiated from 'typename T::sig >::type boost::lambda::lambda_functor<Base>::operator()(A&) const [with A = const bignum, T = boost::lambda::lambda_functor_baseboost::lambda::ifthenelsereturn_action, boost::tuples::tupleboost::lambda::equal_action, boost::tuples::tuple , 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> > >, const int, boost::lambda::lambda_functor >, 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> >]' ../pp_datatypes.h:454: instantiated from 'std::string

I use a few lambdas in my application. Simple ones like (_1 + 1) work fine. However, when I use this next one, the compile blows up on me and produces a huge and indecipherable error: if_then_else_return(_1 == 0, 64, _1) Yields: cc1plus: warnings being treated as errors /usr/include/boost/lambda/if.hpp: In member function 'RET boost::lambda::lambda_functor_baseboost::lambda::ifthenelsereturn_action, Args>::call(A&, B&, C&, Env&) const [with RET = const bignum&, A = const bignum, B = const boost::tuples::null_type, C = const boost::tuples::null_type, Env = const boost::tuples::null_type, Args = boost::tuples::tupleboost::lambda::equal_action, boost::tuples::tuple pp_transform_datatype::evaluate(const pp_value&) const [with Tdefunc = boost::lambda::lambda_functorboost::lambda::ifthenelsereturn_action, boost::tuples::tupleboost::lambda::equal_action, boost::tuples::tuple

, 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> > >, const int, boost::lambda::lambda_functor >, 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> > >, Tenfunc = boost::lambda::lambda_functorboost::lambda::minus_action, boost::tuples::tuple , 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> > >]' cpuid/generic_device.cpp:915: instantiated from here /usr/include/boost/lambda/if.hpp:315: warning: returning reference to temporary

(this is with GCC 4.x) and _1 is a GMPXX bignum So I tried to boil it down, and I ran into a slightly different error. This code: #include #include #include <iostream> using namespace boost::lambda; int real_func(int x) { return x+10; } struct functor { int operator()(int x) { return x+20; } }; template <typename T> struct functor_templ { T operator()(T x) { return x+30; } }; template <typename T> int call_this(T func) { return func(make_const(0)); } int main() { int a = call_this(&real_func); if (a != 10) std::cerr << "a != 10" << std::endl; int b = call_this(functor()); if (b != 20) std::cerr << "b != 20" << std::endl; int c = call_this(functor_templ<int>()); if (c != 30) std::cerr << "c != 30" << std::endl; int x = call_this(_1+40); if (x != 40) std::cerr << "x != 40" << std::endl; int y = call_this(if_then_else_return(_1 == 0, 50, _1)); return 0; } blows up on the if_then_else_return: lambda_crap.cpp: In function 'int call_this(T) [with T = boost::lambda::lambda_f unctor, boost::tuples::tuple, boost::tuples::tuple >, const int, boost::tuples::null_type, boost::tuples::null _type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_t ype, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_typ e> > >, const int, boost::lambda::lambda_functor > , boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, bo ost::tuples::null_type> > >]': lambda_crap.cpp:49: instantiated from here lambda_crap.cpp:35: error: cannot convert 'const boost::lambda::detail::return_t ype_deduction_failure >' to 'int' in return /usr/include/boost/lambda/if.hpp: In member function 'RET boost::lambda::lambda_ functor_baseboost::lambda::ifthenelsereturn_action , Args>::call(A&, B&, C&, Env&) const [with RET = const boost::lambda::detail::r eturn_type_deduction_failure >, A = const int, B = const boos t::tuples::null_type, C = const boost::tuples::null_type, Env = const boost::tup les::null_type, Args = boost::tuples::tuple, boost::tuples::tuple >, const int, boost::tuples::null_type, boost::tuples::null_type, b oost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boo st::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >, const int, boost::lambda::lambda_functor >, boost: :tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::t uples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tup les::null_type>]': /usr/include/boost/lambda/detail/lambda_functors.hpp:148: instantiated from 't ypename T::sig >::type boost::lambda::lambda_functor<Base>::o perator()(A&) const [with A = const int, T = boost::lambda::lambda_functor_base< boost::lambda::other_actionboost::lambda::ifthenelsereturn_action, boost::tupl es::tupleboost::lambda::equal_action, boost::tuples::tuple >, const int, boost:: tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tu ples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tupl es::null_type, boost::tuples::null_type> > >, const int, boost::lambda::lambda_f unctor >, boost::tuples::null_type, boost::tuples: :null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::n ull_type, boost::tuples::null_type, boost::tuples::null_type> >]' lambda_crap.cpp:35: instantiated from 'int call_this(T) [with T = boost::lambd a::lambda_functorboost::lambda::ifthenelsereturn_action, boost::tuples::tupleboost::lambda::equal_action, boost::tuples::tuple