-
Provide a range for your return type, for example:
#include <boost/range/adaptor/argument_fwd.hpp>
#include <boost/range/iterator_range.hpp>
#include <boost/iterator/transform_iterator.hpp>
template<typename Value>
class replace_value
{
public:
typedef const Value& result_type;
typedef const Value& argument_type;
replace_value(const Value& from, const Value& to)
: m_from(from), m_to(to)
{
}
const Value& operator()(const Value& x) const
{
return (x == m_from) ? m_to : x;
}
private:
Value m_from;
Value m_to;
};
template<typename Range>
class replace_range
: public boost::iterator_range<
boost::transform_iterator<
replace_value<typename boost::range_value<Range>::type>,
typename boost::range_iterator<Range>::type> >
{
private:
typedef typename boost::range_value<Range>::type value_type;
typedef typename boost::range_iterator<Range>::type iterator_base;
typedef replace_value<value_type> Fn;
typedef boost::transform_iterator<Fn, iterator_base> replaced_iterator;
typedef boost::iterator_range<replaced_iterator> base_t;
public:
replace_range(Range& rng, value_type from, value_type to)
: base_t(replaced_iterator(boost::begin(rng), Fn(from,to)),
replaced_iterator(boost::end(rng), Fn(from,to)))
{
}
};
-
Implement a holder class to hold the arguments required to construct
the RangeAdaptor. The holder combines multiple parameters into one
that can be passed as the right operand of
operator|()
.
template<typename T>
class replace_holder : public boost::range_detail::holder2<T>
{
public:
replace_holder(const T& from, const T& to)
: boost::range_detail::holder2<T>(from, to)
{ }
private:
void operator=(const replace_holder&);
};
-
Define an instance of the holder with the name of the adaptor
static boost::range_detail::forwarder2<replace_holder>
replaced = boost::range_detail::forwarder2<replace_holder>();
-
Define
operator|
template<typename SinglePassRange>
inline replace_range<SinglePassRange>
operator|(SinglePassRange& rng,
const replace_holder<typename boost::range_value<SinglePassRange>::type>& f)
{
return replace_range<SinglePassRange>(rng, f.val1, f.val2);
}
template<typename SinglePassRange>
inline replace_range<const SinglePassRange>
operator|(const SinglePassRange& rng,
const replace_holder<typename boost::range_value<SinglePassRange>::type>& f)
{
return replace_range<const SinglePassRange>(rng, f.val1, f.val2);
}