Re: [Boost-users] [Fusion] transform / transform_view / binary sequence iteration

Subject: Re: [Boost-users] [Fusion] transform / transform_view / binary sequence iteration
From: Hicham Mouline (hicham_at_[hidden])
Date: 2010-03-02 07:44:36

-----Original Message-----
From: "Thomas Taylor" [thomas.taylor_at_[hidden]]
Date: 02/03/2010 11:49 AM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Fusion] transform / transform_view / binary sequence
        iteration

Hi!

Started out with tuple but soon moved to fusion as it suits my needs much 
better, so thanks for fusion!

My problem is the following:

list<A,B,C> seq2(1,2,3);
list<W<A>,W<B>,W<C> > seq1;

struct fa
{
  typedef unsigned int  result_type;
  template <typename S1, typename S2>
  result_type operator()(const S1& s1, const S2& s2) const
  {
    return s1(s2); // this calls W<A>(A), W<B>(B), W<C>(C)
  }
};

struct fb
{
  typedef std::vector<unsigned int>  result_type;
  template <typename T>
  result_type operator()(const result_type& a, const T& t) const
  {
    result_type a2(a);
    a2.push_back(t);
    return a2;
  }
};

accumulate( transform(seq1,seq2,fa()),fb() );
/* The above yields an error:
no matching function for call to 
‘accumulate(boost::fusion::transform_view<const 
boost::fusion::list<W<double>, W<double>, W<double>, boost::fusion::void_, 
boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, 
boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>, const 
boost::fusion::list<double, double, double, boost::fusion::void_, 
boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, 
boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>, 
database::histogram::fb>) */

How can I use a transform_view (the result of transform(S1,S2,F)) as input 
for accumulate?

Thank you,
Thomas

_______________________________________________

In my basic experience, this has been a matter of constness.
Checkout fusion docs and make sure you follow exactly the function signatures.

Oh! you need an initial state for accumulate()

rds,