[iterator || function_types] zip_iterator -> unpack and call?
Hi, Say I have a function "int add(int, int)" and want to use it in a call to std::transform with zip_iterators. Is there a way to do it without writing an intermediate function object? If not, would it be sensible to write a generic one using the function_types library? I can't imagine this would be too hard but just wanted to know if there is anything I can leverage before writing it myself. Thanks in advance, Sohail
Sohail Somani wrote:
Hi,
Say I have a function "int add(int, int)" and want to use it in a call to std::transform with zip_iterators. Is there a way to do it without writing an intermediate function object?
If not, would it be sensible to write a generic one using the function_types library? I can't imagine this would be too hard but just wanted to know if there is anything I can leverage before writing it myself.
I guess what you're looking for is... http://tinyurl.com/26t9dd =http://lists.boost.org/Archives/boost/2007/01/115135.php http://tinyurl.com/y9ax7t =http://boost.cvs.sourceforge.net/boost/boost/boost/iterator/zip_iterator.hpp?view=log&pathrev=zip_iterator_fusion It seems not so easy because of the Forwarding Problem. Regards, -- Shunsuke Sogame
Thank you, I'll take a look. -----Original Message----- From: boost-users-bounces@lists.boost.org on behalf of shunsuke Sent: Fri 2/16/2007 7:36 AM To: boost-users@lists.boost.org Subject: Re: [Boost-users] [iterator || function_types] zip_iterator ->unpack and call? Sohail Somani wrote:
Hi,
Say I have a function "int add(int, int)" and want to use it in a call to std::transform with zip_iterators. Is there a way to do it without writing an intermediate function object?
If not, would it be sensible to write a generic one using the function_types library? I can't imagine this would be too hard but just wanted to know if there is anything I can leverage before writing it myself.
I guess what you're looking for is... http://tinyurl.com/26t9dd =http://lists.boost.org/Archives/boost/2007/01/115135.php http://tinyurl.com/y9ax7t =http://boost.cvs.sourceforge.net/boost/boost/boost/iterator/zip_iterator.hpp?view=log&pathrev=zip_iterator_fusion
shunsuke wrote:
Sohail Somani wrote:
Hi,
Say I have a function "int add(int, int)" and want to use it in a call to std::transform with zip_iterators. Is there a way to do it without writing an intermediate function object?
If not, would it be sensible to write a generic one using the function_types library? I can't imagine this would be too hard but just wanted to know if there is anything I can leverage before writing it myself.
I guess what you're looking for is...
http://tinyurl.com/26t9dd =http://lists.boost.org/Archives/boost/2007/01/115135.php
http://tinyurl.com/y9ax7t =http://boost.cvs.sourceforge.net/boost/boost/boost/iterator/zip_iterator.hpp?view=log&pathrev=zip_iterator_fusion
It seems not so easy because of the Forwarding Problem.
Forwarding doesn't seem a problem to me since you already have the argument
tuple. The return type inference is painful to get right, though. On the
surface it seems as easy as
template
Peter Dimov wrote:
shunsuke wrote:
Sohail Somani wrote:
Hi,
Say I have a function "int add(int, int)" and want to use it in a call to std::transform with zip_iterators. Is there a way to do it without writing an intermediate function object?
If not, would it be sensible to write a generic one using the function_types library? I can't imagine this would be too hard but just wanted to know if there is anything I can leverage before writing it myself. I guess what you're looking for is...
http://tinyurl.com/26t9dd =http://lists.boost.org/Archives/boost/2007/01/115135.php
http://tinyurl.com/y9ax7t =http://boost.cvs.sourceforge.net/boost/boost/boost/iterator/zip_iterator.hpp?view=log&pathrev=zip_iterator_fusion
It seems not so easy because of the Forwarding Problem.
Forwarding doesn't seem a problem to me since you already have the argument tuple. The return type inference is painful to get right, though. On the surface it seems as easy as
template
... unpack_and_call( F f, Tp const & tp ) { return unpack_and_call_( tuple_size<Tp>(), f, tp ); } template
... unpack_and_call_( mpl::int_<0>, F f, Tp const & tp ) { return f(); } template
... unpack_and_call_( mpl::int_<1>, F f, Tp const & tp ) { return f( get<0>(tp) ); } // and so on
but the ... part is more involved if one decides to use result_of. boost::bind-style inference is of course easier since it only needs to look at F.
Right. I have ever written such codes :-) I should say " *pack*_and_call is not so easy. ". Regards, -- Shunsuke Sogame
participants (3)
-
Peter Dimov -
shunsuke -
Sohail Somani