Re: [Boost-users] fusion: work of 4 sequences at the same time

Subject: Re: [Boost-users] fusion: work of 4 sequences at the same time
From: Hicham Mouline (hicham_at_[hidden])
Date: 2010-02-18 13:05:08

> -----Original Message-----
> From: Hicham Mouline [mailto:hicham_at_[hidden]]
> Sent: 18 February 2010 17:38
> To: 'boost-users_at_[hidden]'
> Subject: fusion: work of 4 sequences at the same time
> 
> Hi,
> 
> I am trying to apply fusion::for_each on a sequence, but inside the unary
> functor applied to each element, I need to know the index of the element
in
> question, because I need to extract elements with the same index from
other
> sequences.
> 
> fusion::vector<...> fseq1;
> fusion::vector<...> fseq2;
> fusion::vector<...> fseq3;
> fusion::vector<...> fseq4;
> 
> fusion::for_each( fseq1, functor<...>(fseq2, fseq3, fseq4) );
> 
> template <typename Seq2, typename Seq3, typename Seq4)
> struct functor {
>   /// ctor
> 
>   template <typename T>
>   void operator()( const T& t) const
>   {
>       /// find out index of t in fseq1,
>       /// use elements from fseq2,3,4 at the same index
>   }
> };
> 
> I could use boost::fusion::find to get an iterator and then get its index,
but
> this doesn not look clean,
> 
> Any ideas,
> 
> Rds,
> 
Ah!

fusion::zip is my friend.

fusion::for_each( fusion::zip(fseq1, fseq2, fseq3, fseq4), functor() );

Could u confirm though that I will be able to modify fseq1, even through the
zipping?

Rds,