zip_view

Synopsis

template<
      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.

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

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.

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> > ));