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# zip_view

### Synopsis

    template<
          typename Sequences
        >
    struct zip_view
    {
        // unspecified
        // ...
    };

### Description

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.

### Header

    #include <boost/mpl/zip_view.hpp>

### Model of

- Forward Sequence

### Parameters

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
--- | ---

    zip_view<seq>
    zip_view<seq>::type

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`.

`size<v>::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.

### Example

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