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Front Page / Sequences / Views / zip_view



      typename Sequences
struct zip_view
    // unspecified
    // ...


Provides a "zipped" view onto several sequences; that is, represents several sequences as a single sequence of elements each of which, in turn, is a sequence of the corresponding Sequences' elements.


#include <boost/mpl/zip_view.hpp>

Model of


Parameter Requirement Description
Sequences A Forward Sequence of Forward Sequences Sequences to be "zipped".

Expression semantics

The semantics of an expression are defined only where they differ from, or are not defined in Forward Sequence.

In the following table, v is an instance of zip_view, seq a Forward Sequence of n Forward Sequences.

Expression Semantics
A lazy Forward Sequence v such that for each i in [begin<v>::type, end<v>::type) and for each j in [begin<seq>::type, end<seq>::type) deref<i>::type is identical to transform< deref<j>::type, deref<_1> >::type.

The size of v; size<v>::value is equal to

deref< min_element<
      transform_view< seq, size<_1> >
    >::type >::type::value;

linear complexity; see Forward Sequence.


Element-wise sum of three vectors.

typedef vector_c<int,1,2,3,4,5> v1;
typedef vector_c<int,5,4,3,2,1> v2;
typedef vector_c<int,1,1,1,1,1> v3;

typedef transform_view<
      zip_view< vector<v1,v2,v3> >
    , unpack_args< plus<_1,_2,_3> >
    > sum;

BOOST_MPL_ASSERT(( equal< sum, vector_c<int,7,7,7,7,7> > ));

See also

Sequences, Views, filter_view, transform_view, joint_view, single_view, iterator_range