Mark Santaniello (AMD) wrote:

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template< typename T > boost::function<T(T)> foo( T n_ ) { //Works, but leaks n //T *n = new T( n_ );

//Doesn't work boost::shared_ptr<T> n( new T(n_) );

return ( *n += _1 );

I think that you need to wrap n in boost::lambda::constant:

return *constant(n) += _1;

Without it, *n is evaluated immediately.

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Peter,

Thanks for the reply. I must be doing something dumb, because now I'm getting a build error.

I think this *might* be the important part: /usr/include/boost/detail/is_incrementable.hpp:59: error: no match for 'operator++' in

'++boost::detail::is_incrementable_::impl<boost::shared_ptr<int> >::x'

Apparently, boost::detail::is_incrementable doesn't work on your compiler; this in turn breaks boost::indirect_reference and the return type deduction for lambda's operator*. But I should also note that *constant(n) += _1 doesn't seem to work even when the compiler supports is_incrementable, because for some reason, Lambda thinks that dereferencing a const pointer yields a const reference.

return ret<int&>( *constant(pn) ) += _1;

compiles for me, though.

Ahh, thanks Peter this helps a ton. Seems like gcc 4.0.2 doesn't like is_incrementable. I tried gcc 3.3.6, however, and it worked fine. I also had success with MSVC 8.0. -Mark