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filter_view

Description

filter_view is a view into a subset of its underlying sequence's elements satisfying a given predicate (an MPL metafunction). The filter_view presents only those elements for which its predicate evaluates to mpl::true_.

Header

#include <boost/fusion/view/filter_view.hpp>
#include <boost/fusion/include/filter_view.hpp>

Synopsis

template <typename Sequence, typename Pred>
struct filter_view;

Template parameters

Parameter

Description

Default

Sequence

A Forward Sequence

Pred

Unary Metafunction returning an mpl::bool_

Model of

Notation

F

A filter_view type

f, f2

Instances of filter_view

s

A Forward Sequence

Expression Semantics

Semantics of an expression is defined only where it differs from, or is not defined in Forward Sequence.

Expression

Semantics

F(s)

Creates a filter_view given a sequence, s.

F(f)

Copy constructs a filter_view from another filter_view, f.

f = f2

Assigns to a filter_view, f, from another filter_view, f2.

Example

using boost::mpl::_;
using boost::mpl::not_;
using boost::is_class;

typedef vector<std::string, char, long, bool, double> vector_type;

vector_type v("a-string", '@', 987654, true, 6.6);
filter_view<vector_type const, not_<is_class<_> > > view(v);
std::cout << view << std::endl;

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