, 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::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/lambda_functors.hpp:148: instantiated from 'typename T::sig<boost::tuples::tuple<A&, 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, boost::tuples::null_type> >::type boost::lambda::lambda_functor<Base>::operator()(A&) const [with A = const bignum, T = boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::ifthenelsereturn_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::relational_action<boost::lambda::equal_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1> , 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::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> >]' ../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_base<boost::lambda::other_action<boost::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::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::relational_action<boost::lambda::equal_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1> pp_transform_datatype<Tdefunc, Tenfunc>::evaluate(const pp_value&) const [with Tdefunc = boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::ifthenelsereturn_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::relational_action<boost::lambda::equal_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>

, 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::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> > >, Tenfunc = boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::arithmetic_action<boost::lambda::minus_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1> , 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 <boost/lambda/lambda.hpp> #include <boost/lambda/if.hpp> #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::lambda::lambda_functor_base<boost::lambda::other_action<boost::lam bda::ifthenelsereturn_action>, boost::tuples::tuple<boost::lambda::lambda_functo r<boost::lambda::lambda_functor_base<boost::lambda::relational_action<boost::lam bda::equal_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::la mbda::placeholder<1> >, 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::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, 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<boost::lambda::detail::return_type_2_ifthenelsereturn<1, t rue, true, false, const int, const int&> >' to 'int' in return /usr/include/boost/lambda/if.hpp: In member function 'RET boost::lambda::lambda_ functor_base<boost::lambda::other_action<boost::lambda::ifthenelsereturn_action> , Args>::call(A&, B&, C&, Env&) const [with RET = const boost::lambda::detail::r eturn_type_deduction_failure<boost::lambda::detail::return_type_2_ifthenelseretu rn<1, true, true, false, const int, const int&> >, 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::lambda::lambda_functor<boost: :lambda::lambda_functor_base<boost::lambda::relational_action<boost::lambda::equ al_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::pl aceholder<1> >, 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::lambda::placeholder<1> >, 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<boost::tuples::tuple<A&, 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, boost::tuples::nul l_type, boost::tuples::null_type> >::type boost::lambda::lambda_functor<Base>::o perator()(A&) const [with A = const int, T = boost::lambda::lambda_functor_base< boost::lambda::other_action<boost::lambda::ifthenelsereturn_action>, boost::tupl es::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost ::lambda::relational_action<boost::lambda::equal_action>, boost::tuples::tuple<b oost::lambda::lambda_functor<boost::lambda::placeholder<1> >, 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::lambda::placeholder<1> >, 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_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action <boost::lambda::ifthenelsereturn_action>, boost::tuples::tuple<boost::lambda::la mbda_functor<boost::lambda::lambda_functor_base<boost::lambda::relational_action <boost::lambda::equal_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>

, const int, boost::tuples::null_type, boost::t uples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tup les::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuple s::null_type> > >, const int, boost::lambda::lambda_functor<boost::lambda::place holder<1> >, boost::tuples::null_type, boost::tuples::null_type, boost::tuples:: null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::nu ll_type, boost::tuples::null_type> > >]' lambda_crap.cpp:49: instantiated from here /usr/include/boost/lambda/if.hpp:315: error: conversion from 'const int' to non- scalar type 'const boost::lambda::detail::return_type_deduction_failure<boost::l ambda::detail::return_type_2_ifthenelsereturn<1, true, true, false, const int, c onst int&> >' requested make: *** [lambda_crap] Error 1

How can I do this? I want to write a lamba that simply says "if (_1 == 0) return 64; else return _1; Thanks!! Tim