assign_each_nonzero.hpp

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// Software License for MTL
// 
// Copyright (c) 2007 The Trustees of Indiana University. All rights reserved.
// Authors: Peter Gottschling and Andrew Lumsdaine
// 
// This file is part of the Matrix Template Library
// 
// See also license.mtl.txt in the distribution.

#ifndef MTL_ASSIGN_EACH_NONZERO_INCLUDE
#define MTL_ASSIGN_EACH_NONZERO_INCLUDE

#include <boost/numeric/mtl/utility/tag.hpp>
#include <boost/numeric/mtl/utility/range_generator.hpp>


namespace mtl {


template <typename Vector, typename Functor>
inline void assign_each_nonzero(Vector& v, const Functor& f, tag::vector)
{
    typedef typename traits::range_generator<tag::iter::nz, Vector>::type iterator;
    for (iterator i= begin<tag::iter::nz>(v), iend= end<tag::iter::nz>(v); i != iend; ++i)
	*i= f(*i);
}


template <typename Matrix, typename Functor>
inline void assign_each_nonzero(Matrix& m, const Functor& f, tag::matrix)
{
    typename traits::value<Matrix>::type     value(m); 

    typedef typename traits::range_generator<tag::major, Matrix>::type     cursor_type;
    typedef typename traits::range_generator<tag::nz, cursor_type>::type   icursor_type;

    for (cursor_type cursor = begin<tag::major>(m), cend = end<tag::major>(m); cursor != cend; ++cursor) 
	for (icursor_type icursor = begin<tag::nz>(cursor), icend = end<tag::nz>(cursor); 
	     icursor != icend; ++icursor)
	{
	    // lambda expressions need reference and property map returns only const values
	    // awfully inefficient
	    typename Collection<Matrix>::value_type tmp= value(*icursor);
	    value(*icursor, f(tmp));
	}

#if 0
    // Iterators are only defined for dense matrices
    // It is not sure if iterators will also be defined for sparse matrices.
    typedef typename traits::range_generator<tag::major, Matrix>::type  cursor_type;
    typedef typename traits::range_generator<tag::iter::nz, cursor_type>::type iterator;

    for (cursor_type cursor = begin<tag::major>(m), cend = end<tag::major>(m); cursor != cend; ++cursor) 
	for (iterator i= begin<tag::iter::nz>(cursor), iend= end<tag::iter::nz>(cursor); i != iend; ++i)
	    *i= f(*i);    
#endif
}


/// Assign \p f(i) to each non-zero i in collection \p c
template <typename Collection, typename Functor>
inline void assign_each_nonzero(Collection& c, const Functor& f)
{
    assign_each_nonzero(c, f, typename traits::category<Collection>::type());
}

} // namespace mtl

#endif // MTL_ASSIGN_EACH_NONZERO_INCLUDE