[boost] [parameter] function types as named template parameters?

Subject: [boost] [parameter] function types as named template parameters?
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-01-22 17:15:10

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Does Boost.Parameter support function types as named template type parameters?  
I'm trying to write a metafunction which lets you use Boost.Parameter to 
specify the template types for a boost::signals2::signal using named type 
parameters, as was suggested during the review.  But it doesn't seem to work 
for the "Signature" function type.  I get errors like:

/home/fhess/svn/boost/boost/parameter/aux_/arg_list.hpp:264: error: function 
returning a function
/home/fhess/svn/boost/boost/parameter/aux_/arg_list.hpp:270: error: function 
returning a function
/home/fhess/svn/boost/boost/parameter/aux_/arg_list.hpp:352: error: function 
returning a function
/home/fhess/svn/boost/boost/parameter/aux_/arg_list.hpp:359: error: function 
returning a function
/home/fhess/svn/boost/boost/parameter/aux_/arg_list.hpp:365: error: function 
returning a function

I can get it to work if I don't use Boost.Parameter for the "Signature" type, 
but only use it for the other 6 types.

Also, I noticed BOOST_PARAMETER_MAX_ARITY defaults to 5, but signals2::signal 
has 7 parameters.  I can't reliably redefine BOOST_PARAMETER_MAX_ARITY in my 
library header, since it must be defined before boost/parameter/config.hpp 
gets included.  You can't redefine the arity and then re-include the 
parameter library headers like you can with Boost.Function.
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